Rasp will only last for about 5 minutes untill the engine/piping warms up. I think alot of people have had good results eliminating rasp by swaping the resonator (bullet or edelbrock) and then removing the exhaust...hope that helped.
99 Tropic Green CSVT KKM Intake 17 TSW Imolas Removed Resonator To Do List: Eibach Pro Kit Diablo Chip(I think)
