I was actually thinking that I should have tried this kind of muffler:
http://www.pickupspecialties.com/Aer...truck_2525.htm
I have the Magnaflow on my 5.3L as well but, had to put a High Flow Flowmaster Resonator on it to help with the in cabin resonance. At 1500 RPM it was unbearable in the cab. I was NOT Happy. If I was to do it again I would try the Aeroturbine or stick with Flowmaster...