Ok, heres the skinny on the Jeep Flashpaq 3870 for the 4.7 WJ.
I filled up with 93 last 2 fill ups (we dont have 91 here, so thats what it gets).
Plugged tuner into computer to update, 20 min later, it has newest version (Spark).
Ran base line testing.
Followed directions exactly and installed just the basic 91oct performance tune. 10 min later, new tune installed.
Not bad for a NA engine.
My GTECH measure 0-60 time average over 4 runs back and forth right before tune as 7.15 seconds with full fuel and spare and me, and a best of 7.12. (granted I do have an excellent running WJ right now). Following the Tune, I averaged 6.71, with a best of 6.69. So it brings a standard 4.7 to the HO mark, which makes sense since they claim 20hp gain.
Driveablitly is what impressed me. Smoother power delivery/idle, and better throttle response, and better shifting.
Now keep in mind, I bought this primarly for the ability to adjust speedo for tire size. The WJ is not a vehicle you should worry about MPG with, if you do, you bought the wrong vehicle, plain and simple. The tune is not super noticable in the seat of your pants, it might be there, but probably just placebo effect. Again, with premium gas its only 20hp, not much on a 4500lb suv.
As for the argument running premium, well the 87 tune only nets you about 6-7hp according to SC. So go for the 91. If you are worried about gas costs, think of it this way. If you fill up once per week and put the max 20 gallons, premium is 20 cents extra. So thats $4 per fill up, or 208 bucks a year, hardly a big deal.
As for the Gtech, its dead on. Matched perfectly with my old S4 at the drag strip, and has matched everything its been on at the drag strip within 1%. So the times and comparison are very accurate.
Overall, if you want a little extra oomph, and a smoother running vehicle, get it, plus it has some fun stuff to play with, and Kolak has good pricing on it.
I am looking forward to the speedo adjuster personally.
2002 WJ Ltd. QD, 4.7L. , Superchips, Magnaflow 12256 muffler and custom 3 inch piping, 2" IRO springs, Procomp 9000 Shocks, JK Moabs, 265/65/17 tires, Moog SS.
Diff fluid change DIY, http://www.jeepforum.com/forum/f310/official-diff-fluid-change-diy-1534883/