I just got mine a couple of days ago. Only played with it on the commute to/from work. Good grief, people sure look at you funny when you keep pulling over and then doing 0-60mph merges back into traffic... !
It's a pretty cool little box, but I can't speak for accuracy. Seems right from what I can tell, and the principals on which it operates are elegantly simple. Accelleration over time. That's it. Now I just need to get on a scale with a full tank of fuel so I can ballpark the HP ratings.
And I can tell that my bone-stock 2001 is going to need a few toys so we can improve the numbers...
For $130 you can't have much more fun. And if you charge your PowerChoke buddies $10 for each time they borrow it, it'll pay for itself soon enough!
JimD