Rattling noise at coast?! Dude!

Hey all. I need some help here. My 95 GSR makes this EXTREMELY annoying rattling noise as I am coasting and not accelerating. Seems only to happen in between 1st and 2nd and sometimes 3rd. The noise is comming from under the car but I cant pinpoint it. What could it be? I took it to the Acura Dealer and they looked at it...they found that the muffler was rusted all the way through (right behind it where it connects to the pipe) and that was what the problem was...they were wrong. I took it to a muffler shop where they did the repair and did some welding and still I have the same annoying rattling noise. It has progressed more over the past few days and I have not yet had time to go back to the Acura Dealer. Any help would be apreciated. I have a Greddy SP exhaust on my Teg. I believe it is discontinued now though. Someone said it may be the whole exhaust set up and that I should invest on getting a new system...I dont know though...Thanks for any help.