Hey, Do anyone know what the stock piping size on the B5's 1.8T would be?
If I threw on a 3 Inch downpipe would it fit with the stock exhaust system?

 

i believe it is 2.25"

 

I'm quoting the newbie guide which you should have already read, "all catbacks are 2.17"

 

Do the whole exhaust. It would be like being 6 feet tall in a 5 foot tall room if you only did the downpipe but not the rest...

 

Stock down pipe is less then 2" and there is a flat spot after the stock flex pipe which is larger then the DP but smaller then the rest of the exhaust.

It would be pointless to do a 3" down pipe on a stock exhaust and a stock cat.