I just replaced my 1 7/8 - 1 3/4 stepped Dynatech headers with slip on merge collectors with 1 7/8 QTPs with welded on merge collectors.
The QTPs are excellent headers. The driver side header fits much better than the Dynatech as far as clearance. I think I may have lost half an inch on the passenger side.
The only problem with the QTPs was the #1 Primary was in strong contact with the steering shaft. Apparently these cars have a few different steering shafts so most people probably don't have this problem. LLoyd at MTI grinded down the shaft for me a good amount and it still wasn't enough, I ground it down some more and it clears now.
Barry at QTP was very helpfull, awesome guy.
I didn't get a chance to dyno before the install but I still have some interesting numbers.
From my old setup (dynatechs, 3" true dual with x pipe) to the new one (QTPs, 3" - 3.5" Y with single 3.5" QTP cutout) I gained about 2 HP across the band. Not bad! I don't have any torque numbers for the new setup. The new setup is dead silent compared to the old one when the cutout is closed. MTI built an excellent Y-pipe, the QTP cutout is too much fun.
The QTPs welded on merge was worth it in itself. The Dynatech slip ons leaked terribly.
Thanks to MTI for working me in (can't praise them enough every time they work on my car, they have to be the most proffesional shop ever), to LLoyd for solving my fitment issue, and to Barry at QTP for all of his help.
Overall these are the best headers around for a big motor if you want a merge collector. If I can see on Friday I'm gonna head out to HRP. (I'm getting laisik eye surgery on Thursday )
-Justin

 

Oh yeah we also dynoed with the cutout closed. I gain about 25 HP all over the top end with the cutout open, not surprising considering I have the stock SS catback behind it.

 

I bought the QTP 1 3/4" Headers and the fitment was perfect. They fit better than the Hooker LT's did and will not rust. Can't beat QTP.

 

my QTPs slid right in aslo.. i am very happy with them.. great product

 

Man, I'd be real nervous griding down something as important as a steering shaft. I know they are engineered to have a certain factor of safety, but that thing is kinda important.

Either way, sounds like you got some kick *** headers.

 

QTP headers and cut out, the ONLY ones I would put on my car.

Congrats on the new set up.

 

The grinding did not weaken the shaft. Here are some before/after pics...

 

Ah, I see now...that's not nearly as bad as what was going through my head. I was fully expecting to see something about the size of a pencil

 

Mine too. Ditto on the headers (the y-pipe is another animal).