Exhaust Question

[jthokie92]

Okay, I have a 2001 GMC Sierra 2WD, w/ 5.3 engine. A lot of stuff has been done so far, Here's the List (ATI ProCharger P-1SC w/ 8-9lbs boost, Speed-Pro Pistons and Rings, Comp Cams Camshaft, Valve Springs, and Lifters, Edelbrock Ceramic Shorty Headers, B&M Shift Kit and Corvette Servo). Okay, now to my question. With all those mods, I've only replaced the stock muffler with a Flowmaster 40 muffler and it sounds awesome, but still running the stock exhaust pipes. Normal driving it sounds great, nice and loud, but not too obnoxious. I recently took it to a car show and dyno'd at 397.06 RWHP. I need to upgrade the exhaust piping and wanted the absolute largest diameter I could feasably put in. One thought was replacing the stock pipes with ones for a diesel engine, cause those pipes are much larger 4-5" in diameter compared to the 3" aftermarket pipes for the gas engines. What's everyone's thoughts on that and will I run into problems if I go this route. I was also thinking about getting remote exhaust cut outs for the track, etc. Wasn't sure how well those would work as far as HP gains, etc. Thanks...

[willfxp]

Without some backpressure, you'll lose low end torque. Not sure what your powercurve looks like now, you probably don't need to worry. Just a thought!

[asilverblazer]

3" is factory and is respectively large. Going any larger would not be overly beneficial for daily driving. If you only run the extremely high rpm's then it would be more worth it. If it was me I'd leave it. I just installed a cat-back system on my truck, mostly to get rid of the giant arm sticking out behind the rear wheel, and more noise of course, if I got more horsepower, whoo hoo.