Are there any High flow downpipes for 2000 Audi A4 1.8T that retains a catlytic converter. Ive only seen downpipes with no cat.

 

umm.. as far as I know, don't quote me, but I believe the stock downpipe is 2.25"? You can upgrade to a 2.5-3.0" for better "flow" and then put a high-flow cat on it. That's about as good as you're going to get, unless you go with a test pipe.