raspy exhaust!?!?!

[Dragon Talon]

So I'm not the only one? who else has aftermarket exhaust?
Well I went down to the performance muffler shop today and had a compression check done to my exhaust. my pressure was fine, infact better than normal. I asked the guy about the backfire and he told me that it might be a small leak probably somewhere after the cat. he said that my exhaust was flowing through alot and maybe not burning all the fuel. and that there might be just a small leak in the pipe or somthing making cold air go into the exhaust pipes and makeing it backfire. I'm not surprised with the shi##y old pipes I have, so to get new pipe from the cat put in is like $60 and for new exhaust put in is $30, if brought in.
So i'm going with that and see what happens.
anybody have some imput on new exhaust i should install.
doind a double exhaust would do no good, even though i want it. so i think just a 2.5" pipe back to the exhaust and then a 3" tip would do good. what you guys think.. should I do a dual tip exhaust or single tip?

 

[GSGoinFast]

I have a 2.5' custom cat back with a magnaflow street series muffler on the end. i have that same raspy problem. mine is horible when i first start the car, it hisses if i get on it at all, or if im just going normal it starts to hiss around 3k rpm's. but after i drive it for like 10 minutes it goes away and sounds really deep loud and smooth, and only hisses occasionally when i get on it. what is this from? and sorry not really sure what a glass pack or a resonator is. been concetrating my studies to the front end. thanks for your help