Originally posted by 3 plus 1
If you plan on turboing (just basic drag gen 3 kit) and a couple other little mods like 3" exaust and high flow cat, will that mess up the obd2 readings?
So long as you run both of the O^2 sensors - one upstream and one downstream of the high-flow cat- and aren't running a slobbery rich A/F ratio, OBD II and the sniffer should be perfectly happy.
Although my DC4 is still stock insofar as drivetrain is concerned, I have found that with my previous cars, giving the catalytic converter enough "drive time" to build up heat prior to testing helps NoX and CO^2 emissions at idle.
Every little bit helps.