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I have a 2005 Subaru Impreza WRX. This is the USDM model with the 2.0L EJ205 making around 230hp and 5 speed manual transmission. The only mods I have done are an HKS cat back and a stage 1 tune. The car has just under 150,000 kms and has no issues what so ever. I am looking to go stage 2 and am having a hard time deciding between a Invidia cattless or catted dp. I really like the way the cattless sounds and it is much cheaper. No matter what dp I get, it will be paired with COBB SF intake. I'm just wondering if the cattless dp is going to cause boost creep on the turbo/engine and if I am going to run into knock. I would like to get the cattless but I don't really want to run into these problems, especially knock. I know that a pro tune is ideal and if someone could estimate how much that would cost also that would be awesome. If someone could help me out that would be great. Thanks
 

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Go catted. Less issues, no stench, better for the environment, and I doubt you'll feel the difference on the butt dyno.
 

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Hard to argue with the environment piece..but I sure loved the rawness of my catfree WRX's, especially that last one. You could very clearly hear the spoolup of the turbo out of the exhaust pipe, when it was revved, lol.
 

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im probably going catless when i stage 2 my wrx in the spring(sorry Clayton, it has to be done). im not 100% decided yet but from what i gather any aftermarket cat isnt really doing the full job anyway. ive never had a catless car, maybe ill hate it and not keep it like that for long, who knows. and to Rayfields point you can hear the turbo better witch is really awesome.
 

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Let's address an issue: boost creep.

How will OP deal with boost creep?...
 

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SD_GR said:
Let's address an issue: boost creep.

How will OP deal with boost creep?...
The same way he would with a downpipe with an aftermarket catalyst; port the wastegate or go external.
 

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Catted also. It's the right thing to do. I just put a performance downpipe (with cat) on my Buick and the thing is smaller end more free flowing than the OEM cat. I'd imagine the aftermarket performance cats for WRXs are similar. The small difference between no cat and these aftermarket ones seems to say go with the cat and be legal, help the environment, make the car more saleable later, etc.....
 

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im probably going catless when i stage 2 my wrx in the spring(sorry Clayton, it has to be done). im not 100% decided yet but from what i gather any aftermarket cat isnt really doing the full job anyway. ive never had a catless car, maybe ill hate it and not keep it like that for long, who knows. and to Rayfields point you can hear the turbo better witch is really awesome.
This doesn't really get the sound across like it really was, standing beside it, but I couldn't resist posting it. Can anyone tell that I miss this car, yet? :sadwave:
The catback wasn't as smooth as the Cobb I had on my first WRX, but not bad for something sent to me for free by a fellow ClubWRX'er.
..
 

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You've just identified yourself as a "Really Old Forum Guy" to be aware of that. :wiggles:
That was a fun time..that thread where I unveiled my new bugeye, deciding that I wouldn't mod it...and then modding the &$#@ out of it over the next few years. That was now 12 years ago, my friend.
 

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yea i cant really tell witch one i like more, the microphone makes them sound like they are the same volume as well. the 2nd one does seem a bit more wild i guess, if that makes any sense...
 

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You've just identified yourself as a "Really Old Forum Guy" to be aware of that. :wiggles:
That was a fun time..that thread where I unveiled my new bugeye, deciding that I wouldn't mod it...and then modding the &$#@ out of it over the next few years. That was now 12 years ago, my friend.
Ah yep. Applies on both counts.
 

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yea i cant really tell witch one i like more, the microphone makes them sound like they are the same volume as well. the 2nd one does seem a bit more wild i guess, if that makes any sense...
Both are catless downpipe. The first is the stock catback, the 2nd is a custom job. You can't hear the difference? It was quite obvious in person.
 

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im probably going catless when i stage 2 my wrx in the spring(sorry Clayton, it has to be done). im not 100% decided yet but from what i gather any aftermarket cat isnt really doing the full job anyway. ive never had a catless car, maybe ill hate it and not keep it like that for long, who knows. and to Rayfields point you can hear the turbo better witch is really awesome.
My MR2 turbo is catless, and my WRX had a perrin catted downpipe (it passed the sniffer test at inspection fyi), so I have experienced both. With the Catless car, the difference in power is nominal, you can't pass inspection, and when in traffic or starting it up in the garage the stench is atrocious... a raw gas scent that sticks to your clothes and gives you a headache. Plus you're ****ting on the planet we all share as an added bonus. It's fine for the SW20 because it maybe sees 1000 miles a year of sunday cruising etc. But going Catless on a daily driver I just would not reccomend. The one possible real benefit is that tailgaters are likely to back off from the smell coming out of your tailpipe! As for the turbo noise, I noticed more spoolin' sounds by changing out the intake on any given build. YMMV, of course do whatever makes you happy but I would not say there are no downsides to catless setups.
 

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i was not aware that aftermarket cats could ever pass an inspection. NJ dosent do sniffer tests anymore im pretty sure so i would probably pass as long as they dont do a visual inspection. i dont really want to **** on the planet too much, i dont drive a huge amount, my commute is 8 miles. im hoping my time with the car is temporary, if i was smart i would stop with just the ap. im really hoping the next sti will be the first affordable hybrid powertrain sports car. i will be emailing you to reserve mine asap if that becomes true.
 

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rqjoe said:
The small difference between no cat and these aftermarket ones seems to say go with the cat and be legal
An aftermarket downpipe with a high-flow cat is just as illegal as a catless one. You're tampering with emission control device, whether by reducing it's ability to function (catted) or removing it (catless).
 

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An aftermarket downpipe with a high-flow cat is just as illegal as a catless one. You're tampering with emission control device, whether by reducing it's ability to function (catted) or removing it (catless).
Very true. You've thrown legality out the window, the moment you start fiddling with these pipes. I must have run catless downpipes through at least 9 NC inspection cycles. It's an "OBDII Check" county, but I was always a little surprised when no one ever mentioned it at all. I suppose they were rubber-stamping the county/state requirement, and didn't concern themselves with the federal piece?
 

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i was not aware that aftermarket cats could ever pass an inspection. NJ dosent do sniffer tests anymore im pretty sure so i would probably pass as long as they dont do a visual inspection.
I guess in my case they they couldnt tell it was aftermarket or just didn't care. Last time I went for inspection, they did do a visual check on the underside of the car to confirm the cat was there. That was at the state facility in Wayne, independent shops might not check I'm not too sure.
 
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