The check engine problem is not restricted to cars with extended O2 wires or those without cats. I got the check engine light on my '01 car about 1000 miles after installing Belanger headers & catback, even though I was using the stock cats and had not modified the O2 sensor wiring loom. Hennessey says every '00+ car he's seen with headers eventually gets a check engine light. In my case, I solved the problem by switching to a MOPAR ECU.