i have a 99 civic si with a drag gen III turbo and apexi N1 exhaust w/stock cat...i want to take out my cat and put in a test pipe or straight pipe...the places i have aksed wont do it cause its illegal....how hard is it to do? does it just bolt right in or would i need to weld it?

 

you have to search and see if they make test pipes with flanges on it. Why not just get a High flow cat?

 

a few rusted bolts and it's off

 

not hard to take off a cat. all it is is a 3-bolt flange and a 2-bolt flange going to the downpipe. as TEG said you can just get a highflow cat and stay legal, or if you really want to have those extra 4 or 5 horsepower you can just use a test pipe or just get another cat and gut it.

 

if u go test pipe on a obd2 car u will get a check engine light because the o2 in the cat will not read right also might get it with high flow cat

 

I thought if you have an OBD2 and had a test pipe, you could get something that fakes the signal to an O2 sensor???