well for one, if your running a cat, it shouldnt throw a code as long as the cat is FUNCTIONING PROPERLY.
if you have a staged upgrade, it wont throw a code at all, because the downstream 02 sensor which detects the cat, is not used by a staged pcm. a staged pcm only reads the upstream 02 sensor located in the 02 housing right after the turbo.
the only thing sensitive to the computer when it comes to a new exhaust is the presence of a properly functioning cat.