does the jdm 4-1 header affect the stock 02 sensors in the obdII cars, if i wanted to run the jdm 4-1 and a test pipe how could i trick the o2 sensors or would i have to buy an obdI conversion

 

The testpipe will set it off. But the JDM 4-1 won't.

 

ok cool, so if the test pipe will set it off is there a way to trick the ecu or would i need to convert to obdI, or what about a carsound cat i've read that they make an obdII application, how much different would the testpipe be from the carsound cat?

 

testpipe and carsound cat both produces results that are within 1-2hp of each other. I would personally get a high-flow cat to reduce the emission. try http://www.ipsracing.com or SMSP on this for a bolt-on carsound cat for your car.

 

I would get a carsound cat instead of the testpipe. More environment friendly, cop friendly, everything friendly. It's not worth the extra HP unless your doing drag or road racing.

 

I had a test pipe and decided to go w/ a carsound cat and I really couldn't tell a difference between the two. Not worth the hassles of a test pipe IMO...