[DP03]

Don't focus on the diameter of the pipes. 2.75" X 2 is way more than enough to exhaust anything the 6.1 can throw at it.

When I raced my 10 sec LS1 (about 500 crank hp), moving from a single 3" pipe to a single 4" pipe gained absolutely nothing.

Go with the exhaust that you like the sound of most, and be careful of the constuction. I had the JBA on originally (obnoxiously loud inside the car), and found out it had baffled mufflers. My car club did a flow test years ago showing that baffled designs (Flowmaster, at the time) actually flowed less than the stock exhausts. My point here is that louder mufflers do not necessarily flow any better.