[Pyrotechnic]

Headers will give you a little more treble in your exhaust sound versus stock iron manifolds. Iron manifolds really muffle the sound.

A pair of old blown out glasspacks will really give you the raspy sound your are looking for. Just get the cheapest ones you can find and make sure they aren't guaranteed against blowing out.

Drilling holes in your muffler will bring out the treble too.

I personally do not like a wide open exhaust, but this is what I have seen that creates a loud and raspy exhaust.