Their is a lot of negative feedback on this muffler,a cheaper muffler is the Summit turbo $20 a piece [SummitRacing]a great sound from all the feedback.
For all out performance the Edelbrock RPM Muffler about $90 a piece.
I used to have some on my sho,lasted two years and they blew holes every which way.
Rasp comes from freed up exhaust flow like running catless Y-pipe,or no resonator.