Newbie with a few questions for those in the know.

**BK3** · 09-23-2011 05:19 PM

I just bought a 03 WRX (not an STI) just wondering a few things. I believe it is stock as of now, what is the best sounding muffler for it. Also is it ok to run the K&N filter in it. I heard some things about some turbo cars dont do well with the oil in the K&N filters, it meeses up the mass air flow. One last one what type of oil should I run in it, Synthetic? Thanks for any info and help.
Bobby

**SD_GR** · 09-23-2011 05:23 PM

Originally Posted by BK3

I believe it is stock as of now, what is the best sounding muffler for it.

Tastes vary. Go to a meet and listen. My fav is a Stromung but I like money more than I like mufflers so I kept the stock muffler on the car.

Also is it ok to run the K&N filter in it.

On your car, sure; I'd never run one on mine though. I doubt it filters better than a paper OEM filter, and I strongly dislike the oiling process and the potential to mess up the MAF and/or allow more silicon than absolutely necessary into the motor. I therefore use the correct filter specified, not a fancy oiled filter. If I owned your car, I'd still use the correct paper filter specified...

One last one what type of oil should I run in it, Synthetic? Thanks for any info and help.
Bobby

There are several oil threads, look around, but have an eye out for hype and unsubstantiated claims. Look in the owner's manual for the oil specs, and pick an oil that meets those specs exactly. I happen to use Shell 5W-40 but there are numerous other choices.

**Sasquatch** · 09-23-2011 05:28 PM

Greetings and welcome to the Club Bobby!

Great exhaust sound is in the ear of the beholder. There is no substitute for hearing as many as you can in person.

Simply put, K&Ns do not filter as well as an OEM paper filter. Some time ago I happened across an article that was a real eye opener. At the time I was using a K&N - I quickly switched back to OEM after that. I'll see if I can dig the article up ...

I seriously doubt there is any significant measurable power to be had from a K&N in a WRX.

A catless up pipe is highly recommended. The OEM up pipe's catalyst has been known to break into pieces, sending fragments into the turbo. This is bad.