exhaust thread

Hi ppl. Im from South Africa and cannot get much help on our forums here. i recently purchased 2006 Accord Type-S and last week decided to fit custom exhaust (63mm SS) mandrel bent tig welded...frikkin looks the beez neez :up: (will add pics soon) but 3 days ago the engine light went on under...

Hi you can help me with a decision? which tubing is better for a K20A? with rbc Intake Manifold and 200 zeller catalytic. 70mm or 76mm would like to extract the optimum performance from the motor, the exhaust thx greets from germany Daniel