if i go with a downpipe which elminates cat will this bolt up to my stock o2 housing? because sum downpipes are 2.5 inlet then 3in some are full 3in..
2g awd
big16
3in exhuast
thanks for the help :)

If you buy a downpipe for your car, it doesn't matter if it has a cat/testpipe or not. It will bolt right up to your existing 02 housing, there is another option you might consider. There is a downpipe that has a 02 eliminator on it. This means you don't have a 02 housing anymore, the downpipe just has a bung for your O2 sensor in it. Thats the exhaust I have and I like it. So 2.5" and 3.0", it doesn't really matter on how it bolt up to your car.

CRAIG