Called SLP today, they no longer offer dual exhaust for an 89 IROC, so now I'm looking for a second option.

 

Some will agree with me that Hookers Aerochamber catback sounds great. It's not the drone/hollow flowmaster sound that an american thunder or force 2 flowmaster kit will get you.

I'm a big fan of making my own catback...If you're near stock, just for fun I'd do 3" from the cat back..over the axle..Choose any muffler you like and have a single exit. I'd try a 3.5" spiralflow because they are cheap and sound great on LS1 cars. If that's not nice I'd try a 40 series flowmaster...single in/out..maybe even a 3.5/4" version. Goodluck!

 

A buddy of mine in our club has a 90 Iroc with Mufflex exhaust. Baddass

 

Mufflex had the right idea...offer a few different great sounding mufflers along with a few different tubing sizes. They offered the single in/out 4" race flowmaster which is great and also a Spintech.

 

little more info on the car

you near stock?
cats?
built motor?

sounds like you want dual tips.

you could go for the dynomax dual 2.25" side by side exhaust, although i'd stick a magnaflow Xpipe in it.