Exhaust is Raspy

[Bens4runner]

This seems like a stupid Q, but is there anything for cheap i can do to smooth out my exhaust note, i have a flowmaster 50 series muffler and a straight 2.5" off the header that dumps right behind the rear axle, it sounds pretty raspy under decent acceleration and putts or coughs alot under deceleration( while in gear), Is there an exhaust tip that could even the tone or make "cleaner"?
And I know the absent cat is a large cause of this, but the question still remains.

Thanks,:AK47: Ben