Diablosport Predator on the way!

I got a Diablosport Predator, new, on ebay for a good price.. I don't really know what to expect from it. My car is a '98 3.8 auto, mechanical mods are dual Flowmasters, BBK intake, and throttle body spacer. The wheels went from 15 to 16 inch, and that was never corrected, so I know this thing will correct the speedometer. I have read that with automatics it "firms up" the shifts.. does that mean it will slam through the gears? Excuse my ignorance, this is my first flash tuner. With my car and my mods, can I expect a dramatic improvement?
In the future, I plan on getting rear gears and traction-lock, so I know the predator will help with that too. But I am curious what I can expect for now, just with what I already have.

Well since only ONE of you answered me, I'll just TELL you all how it works! With my light modifications, there wasn't a whole heck of a lot of difference. I can tell the shifts are a little firmer, but there wasn't any dramatic improvement in performance. It feels a hair quicker, but it's hardly noticable, and it certainly didn't turn the car into a fire-breathing GT killer. (I wasn't expecting it to, don't flame me for that!) I guess now I'll let a few tanks of premium (92 here in Or-Y-Gahn) go through, and see about the claims that it increases your fuel economy. As for performance, that predator should still help me when I get 3.55 gears and locking rear differential.

PS: I can tell you one thing... the advertised increase of "average 15-20 hp" is pretty much..