new to v6 perfomance so whats up everybody? i'm porting my exhaust manifolds, gasket matching, etc. because i own a cali spec vehicle and headers would eliminate the pre-cats causing ecu probs with air/fuel and o2 sensors. i need some info if anyone can help me out. there is a lip inside each flange which connects to the pre-cats. i want to know if i can remove the lip without any problems? would there be an o-ring of some type between the manifolds and cats? and if so, would removing the lip cause a leak at these connections?