[cipriano]

I have a feeling this is a stupid ? but I need to know. I'm looking at exhaust systems for an 2004 Mustang Mach I. The parts I'm looking at now are the catted SLP Loudmouth II's and I'm undecided on a x-pipe or a h-pipe. Now this is what I'm thinking... The SLP's have a cat and the headers have a cat. Do I need 2? Or do both have a catalatic converter? If they both have cats and I don't need two then can one of them be a Off-Road Pipe and it still be legal in NC?

 

[lucca]

1. cats can be had for long tubes
2. two MIL eliminators (in place of aft O2 sensors) will be needed if you run without cats
3. not all emissions tests require a visual on an OBDII system the computer is tapped into and read (AZ smog procedure), the MIL eliminator will say everything is cool and the cats are there.

 

[ann15]

theres such things as long tube headers which are great for racing, but they arent street legal. if youre thinking about going that route, long tube headers dont need cats, i dont even think they make cats for them.
shorty headers are legal, and the SLP comes with 2 catalytic converters. you need those 2 in order for it to be legal.

 

[tripp]

No, unless you are in a state with smog laws- then yes, you do need them to pass emissions testing.