Muffler questions

I have a 91' Chevy 2500 with a 350 which is bored .040 over and with hedman headers. I just recently put dual exhaust from the headers back, it has no cat on it. I have 2 Flowmaster Original 40 series mufflers ( 2.50" pipe all the way) and it sounds like crap. It sounds nothing like a flowmaster should. Should I cut them off and put glasspacks on it or what? It sounds like a loud noise with a "popping" sound. It annoys me. WHAT SHOULD I DO???!!!
I AM FRUSTRATED!!!!!:banghead: