Im looking to get an aftermarket muffler and i noticed there are different inlet and outlet sizes. does anyone know what sizes mine are on my stock muffler? I have a 95 formula if that helps, thanks.

I put a Hooker AeroChamber muffler on my 94 Formula about six months ago. The part number is 21721HKR. The specs for this muffler state that the inlet is 2.5 in. diameter and the outlets are 2.25. The stock iintermediate pipe and the stock tail pipes will just slip inside of the new mufffler inlet / outlet stubs. This allows you to weld it together once you fit it up. the stubs are also long enough so that if you cut the old muffler off close to the case, you can maintain the stock spacing where the tips come out under the rear bumper.

The Hooker sounds pretty good on the LT1, in my opinion. It isn't much louder than stock, at least on my car, but it definitely sounds better.

Hope that helps.

Stock is 3" inlet and 2.5 exits.

Thanks.