Have a friend that has a 97 GST and he is looking to start modding it. He has found an APEXI down pipe and full catback APEXI exhaust. From what he and myself understand, there is no cat when you use both of these. Will he get a check engine light because I understand there is an o2 sensor after the cat.

Any info would be appreciated. We don't want to see the dreaded CEL unless you guys no a way around it.