Well between my stock SS, and my two friends on the boards, I've been able to drive all 3 different tunes.

The Stage 1 kit is a very noticeable improvement over stock. (I still enjoy the stock form reguardless)

The car would tend to fall on it's face a bit between shifts. I didn't do any no-lifts since it wasn't my car, but the owner said it just pulls like crazy when you grab it, and I believe him. Overall, very happy with it, and you keep your warranty. I'll be doing this upgrade eventually.

Hahn tuned car was a different story. The car spins the tires in 1st effortlessly, something I wasn't able to do in the Stage 1 car. The Hahn also had higher boost and would spool much quicker. I also didn't notice the lag in power between shifts as I did with the Stage 1, probably since I was at higher boost levels.

Overall, amazing cars, all 3. The Hahn was probably the most fun to drive, but since my SS is just a daily driver, I'll probably go with the Stage 1 to keep my warranty.

I don't know if this is a repost, I haven't been on the boards much since I bought my new toy, I've been on those forums, but maybe this would prove interesting to someone.

 

The GMPP stage tune leaves a little low end torque on the table, ostensibly due to the FWD. It's debateable whether increasing it gets you anything tangible in a traction limited car, unless you're adding slicks or drag radials. At that point, say hello to a new clutch and halfshafts.

 

Since my Stage 1 upgrade, I also don't spin tires in 1st anymore (it would shred them before the tune from a roll). I only hit 10 psi in first opposed to 13-14 bone stock. However, 2nd and on it's a different story. I see 20 psi in 2nd and 23 psi in 3rd-5th. A 3rd gear full-pull has the ESC light going nuts...LOL. Apparently the Stage 1 tune "modifies" 1st gear boost for traction.

 

I think that might actually be better. At the local drags I would lose a lot of time to spinning the tires off the line.