The diam attached to the cat is the restriction, not the cat itself. The stock cat can be made to fit a 3" exhuast

 

Whoa...Thanks to everyone! Yeah, the only reason that I wouldn't want to do a test pipe is because of emissions...apparently CO is gettingmore strictabout emissions next year. I also would have a heck of a time getting the test pipe software from APR....I don't have a home programmer for my ECU....but I guess a test pipe is the way to go! I can just swap it for emissions....

 

A couple more questions...How much louder is the stock exhaust with a TP compared to the stockcat? I really don't want my car to be obnoxiously loud (a little growl would benice though )...Second of all, whatcombination of non-foulers has worked for people? If I can't get the APR TP program, I might as well just fool the lambda sensors into thinking there is no problem like most people do .

 

Its only a few more dB louder.

 

how about on a 2.8 B5? i guess a 'test pipe is a turbo thing?

 

I've heard of people doing test pipes on NA cars...It's just not that common. The reason that they are so good on forced induction cars is because the turbo spools a lot easier with no cat, therefore increasing airflow and making it spool sooner. I honestly have never seen it done with a B5 2.8 though...mostly subaru's and honda's...

 

I read on here a while back that its possible to pass emissions with a test pipe if the car is quattro.. is there any truth to this?

 

having quattro has 0 to do with it. The newer cars just get scanned and if there isnt a code or cel, you will pass.

 

Honestly, it probably is possible if you fill up with 5gal of E85 before you get tested . It would be AWESOME if one could do so on 91 octane...I know somebody that passed emissions with a WRX with 2 catsgone and 1 high flow (they have 3 cats to begin with). In response to the scanning of the newer cars, IIRC, Colorado sniffs no matter what...They do a CEL test, scan for codes, and then drive it on the dyno at varying speeds with the sniffer on the tail pipe...This is in Arapahoe county, FYI...Apparently most CO counties don't even do emissions...

 

Anyone in Colorado have any input? Better yet, anyone in Colorado with an test pipe that they don't want ? I really don't want to deal with shipping and would kind of want some kind of preview of the gains...Despite taking physics, I don't exactly knowwhat 15HP and 40Ft*Lbs of torque feels like...