Trying to decide whether to nab a 034 3" test pipe or go spend a little bit less on an ebay 2.5" test pipe. Now, at first I thought that the 3" was a no-brainer but then I thought again that the test pipe is 3", but the down-pipe in my milltek is only 2.5" in diameter. My question is, since the downpipe is only 2.5", won't having the exhaust go from 3" to 2.5" and then to 2.75" be worse, or at least just as well as just going from a 2.5" test pipe to 2.5" down pipe to 2.75" exhaust?

I'm thinking that going from a larger diameter to smaller is going to create back pressure which will restrict flow.




second question:

on their site it states fits 2002-2005 A4 passats.. I'm guessing this is a typo? since it says fits B5s?

 

The flow velocity will choke somewhere in there, I'd recomend a 3" turboback, but since you've done the downpipe already, go ahead and see if you can do a 2.75" testpipe if you can. If not, then 2.5" is fine. The more airflow out, the better.

 

b6 and b5 test pipes are one and the same

if you plan on going with a larger turbo i'd say go with the 3" now

i have a 2.5" and am getting a 3" back done soon, so all i have to do is switch out the test pipe when i go bigger

 

Go 3" with the BT. I had a 2.5 setup on my 98 w/ a k04 and am now going GT28RS with a 3" My exhaust guy said 2.5' or 3" there is no 2.75... If that helps with your decision. Search youtube for a guy with a 3.0" borla I believe, it sounds awesome; not cop lovin...

 

Wont see much of a differnce between 2.5 and 3" on a stock turbo. Having the stock cat made to have a 3" in/out would be cheaper and still keep you legal (if you have emissions). The cat will only rod you of all of 1-2whp on a all out stock turbo setup. It flows really well.