I have a '98 Z28 M6 with a few of the free intake things (the FRA and hollowed out lid...will buy lid soon). As for exhaust, I plan on some coated Pacesetter headers and cutouts with a catted Y-pipe and stock I-pipe/muffler. I love how my cammed LT1 sounds through the cat-less Hooker exhaust I have, but as of now, I want this car to remain stock-like quiet when driving around. That's one of the reasons I bought a 4th gen to replace my 3rd gen. I don't mind the Z28 exhaust but I liked how my friend's '99 SS sounded with his stock exhaust and was curious as to whether there would be any performance difference between the Z28 exhaust and an SS/WS6 exhaust instead (when the cut-outs are closed).

I can get an '02 WS6 cat-back for cheap, so I'm just trying to decide if its going to be noticeable or if I should just keep my exhaust as it is.

 

I wouldnt waste your time going from a stock Z exhaust to a ws6 exhaust. The 'stock' exhaust that put out the most power is the SLP TOL, which was an option on the SS. If you are looking for a stock sound then the TOL is the way to go TOL=Two out of left. It may be that your friends SS had the TOL exhaust, so you might wanna check into that.

 

You say you can get it for cheap... how cheap? Have you factored in the cost of labor, or are you going to do the welding yourself?

 

maybe 5HP..

 

Nah, he didn't have the 2otl, I had that on my thirdgen before I put the Hooker on. He just had the standard dual 2.5" chrome tips. Maybe I'll just put some small stainless tips on my exhaust and be happy with that and put my rectangle tips on my other car.

I'd bolt the rear up myself by the way, its just a slip fit. If I choose to weld it in place, I've got a few friends at shops that'd weld it for me.

 

2otl was only available on the LT1 4th gen SS/Firehawk. The 98up had the dual/dual as an option.
If you want stock like sound, get the dual/dual. I've seen them CHEAP on ebay and for sale local. A hooker catback has very close to the same tone and dB. The plus side is that both of these are larger diameter than stock.

 

The take off exhausts can be had for fairly cheap and it is a slip on like you said (at least at the I pipe). Flows a little better then the Z28 exhaust, if you like the sound then you should go for it.