I'm curious about this also. But I would really like the looks of dual pipes out the rear. Is this doable with a flowmaster 40? I'm looking for a low rumble and something that can make some noise when I step on it. Any help?

 

If you buy a Flowmaster. DUMP IT! You're gay if you run tailpipes after a Flowmaster.

 

I just had the shop here do a full system from my cats out the rear. I had them use 2.25" pipe, and the 14" Magnaflow muffler. The shorter the muffler, the louder it'll be. It's definitely louder than stock, and sounds very good to me, esp. at low RPMs. Over time it'll probably get even louder. I'm also hoping for better fuel economy. Magnaflow out-flows Flowmaster and the competition from what I was told. I'm very pleased with mine so far....I honestly can tell a power difference. My truck doesn't downshift as much to pull up hillsides, etc.