header question... Options

[Antz5SFE]

if i install a header which removes the first cat, can i still pass emissions with just the rear cat?

[Galcobar]

Two issues: whether the inspection includes a visual component which requires you to retain any emissions equipment originally installed (in many jurisdictions it's illegal to remove a working catalytic converter), and secondly; whether your exhaust gases can meet the mandatory levels.

If the first condition it true, then the answer is no (unless the inspector is an idiot or very friendly). The second condition is harder to answer. If your car is in great running condition, then possibly, but not likely. Aside from the loss of catalyst volume, the primary catalytic converter benefits from quickly warming up and operating at a high temperature because it is positioned so close to the exhaust valves.