I have a 99 Honda Accord EX. I have headers (megan) with 2.25" outlet diameter and my cat-back (magnaflow) has the same inlet diameter. I’m trying to find a catalytic converter with a high flow design (and preferably not one that I have to weld) that has the same diameter. All I can find is the resonator 'test pipes' that are not permitted for street use. Anyone know of anything

 

if you are in a area the does NOT have emissions you can use a ebay "high flow cat" (test pipe). Iv been running one as long as I have been building hondas (10years). They say they are only for off road use b/c they aren’t emissions friendly. But if you do have the emissions then you can find high flow cats by flowmaster and magnaflow makes them. But expect to spend some money they aren’t cheap.

 

I hear that if I put one of these 'test pipes' on it will that trigger a error with my 02 sensor. Is this true? Also I know about the 02 simulator (like the ones advertised on ebay), but do those really work?

 

Yes testpipe will trigger O2 code instantly. It cost me only a couple dollars to trick my O2, i was running a test pipe for a while and no check engine light on ever but it sounds very loud,raspy,loose more low end torque and run richer. Any ebay hiflow cat is ok to use and flow better then the stock one.