I've been running the Hartge header system for 2 weeks now without the stock cats. I just have the temporary 16" "test/evaluation" straight pipes between the end of the downtubes and the inlet of the stock resonator.

I've been looking into a pair of compact universal aftermarket cats to weld some flanges on & bolt into the system to make it legal. Anyone have experience with "Car Sound" Magnaflow cats or similar aftermarket universals? They're nice & compact and will fit perfectly and are cheap.

The new headers are plently loud with the stock resonator & rear exhaust so I won't be going to an aftermarket exhaust anytime soon. The stock cat won't work with the new headers and I don't want to butcher them lest I need to put the cast iron headers & stock cat back in if the emission Nazis get pissy with me the next time the emissions test is due.