[Aussie Mike]

I've just about finished an underbody system for my car. Our strict rego laws down here mean that a hand built Cobra is considered to be a new car and must meet all the current design rules. that includes noise and emissions so the system needs to be quiet i.e 90dB @ 2/3 operating RPM measured at about 2 foot from the exhaust tip.

My underbody system uses modified factory dual layer pressed steel headers from the Corvette (LS1 Powered) that run into 2.5" collectors then into cat converters. Out of the cat converters the pipes taper down to 2" and then Y together into a single 2" pipe. This runs into a heavily baffled muffler and then into another resonator before exiting the rear of the vehicle.

we also have to have a minimum of 4" of ground clearance so the suspension gets wound up a bit too.

Not real good for performance but should knock the noise down to legal levels. Needless to say the whole system is designed to be quickly and easily un bolted and be removed so I can bolt my side pipes on (Honestly, I only bolt them on for for track days Officer).

Cheers