Alright, so about a month or two ago I bought a 89 IROC 305 TPI, it already had an aftermarket muffler, some knock off p.o.s., it started making these whistle that if you heard it makes you want to go crazy. So I found a bunch of holes and perferations in the muffler/intermediate pipe. The people at the inspection station said they couldnt get a reading which is crap cause I got plenty of a reading. So needless to say, time for a new catback. I already had a semi-new flowi i picked up for $40. I got the intermediate pipe, which was wrong so I had to have a shop customize for me, so I said just put the whole thing in. Get the car back, no exhaust leaks, but it whistles as if I never changed anything. There is nothing in my motor to cause it. I am thinking maybe in my cat/y pipe? Any info anybody? It drives me crazy, its super loud at low rpms and goes away after 2000. Any help is greatly appreciated.