It's just the type of downpipe. There are two kinds: Bellmouth and Divorced Wastegate. Basically, there is a piece of metal that completely seals off the internal wastegate from the exhaust side of the turbo. It dumps back into the downpipe about 1/2 way down.
Divorced Wastegate DP: http://www.team-ninja.com/vbulletin/...1&d=1049577216 http://www.scoobytuner.com/graphics/invidia_v3.jpg
Regular bellmouth DP: http://spun-autosports.com/sales/ima...d_Downpipe.jpg
It's really all based on personal preference with the DP. I've heard pro's and con's to each. Unless the divorced wastegate DP actually COMPLETELY separates the turbine wheel from the wastegate arm, then it's really not practical. I've also jut been told by my tuner that he prefers bellmouth over divorced. The car is currently inspected, but it doesn't need inspection until...I think March? May? Something like that. But it's just nice to know that I don't have to worry about it for a while. A long while I don't really know of any "good" place to take it. Sorry
Yes, there is a test where they hook a probe up to your car and it literally "sniffs" your exhaust. In Virginia, though, they DO NOT do this test woohoo! I think you will be okay catless. It also depends, IMO, where you go. Usually, the hole-in-the-wall type shops don't really seem to care as much. If you are too worried about emissions though, just go for the catted DP. Also, I would go for a bellmouth instead of the divorced wastegate. Just my .02.
Ah, I see, nice to meet ya! Well, right now I'll pass the visual inspection. I have a catless DP w/ a STi catback (w/ the cats gutted out of it). Even though it is "catless" it still appears to be stock. Haven't had any problems with it. In Virginia, they don't do the "sniffer" test otherwise I'd be screwed haha. But right now, I go to school in NC so I have this thing that I do where I can get a sort of, "pass" for I think up to 6 months until I am back in the state to get my emissions checked which is kinda nice