That "brrrrraaaaaaaaaap!" is the sound your set up makes, and the sound that guys liked back then. I had the same set up as you on my 1 ton, changing to dual intake made no difference. I had 24" cherry bombs on the truck. If you don't like the brap, then actual mufflers is what you want, as has been suggested. I like that brap!
Back firing on deceleration can be reduced by making the idle mixture more rich. But, the truck will still be louder with glasspacks than with mufflers.
