I have the standard GTech Pro unit and it always returned very optimistic numbers. I never trusted it. It also was quite limited in the data it captured. The Competition model offered a few more features but the price was high, and it didn't add THAT much. I found the RaceTech AP-22 to be the best bang for the buck, period. It is INCREDIBLY flexible and it matches times verified by my GPS (speed) and stopwatch (time) which the GTech never did. Cost is about the same as GTech Comp model, but it also measures lateral G's, has tilt compensation, time & distance between any 2 speeds (0-60, 0-100, 30-90, whatever you want) and will do the same for braking (70-0, 90-30, etc). It has a RS-232 serial port for data download to your PC. Oh, and no annoying power cords to plug in! I'm not a sales rep and don't benefit from this, I'm just a very happy customer. Here's lots more data from the only place in the USA that sells, them (
AFAIK):
http://www.cb-racing.com/rt-ap-22.htm
Here's some sample output from 0-60 runs on my diesel, ignore the HP numbers as I hadn't set up the vehicle weight prior to testing so the numbers are all low:
http://www.meimann.com/docs/mercedes/87_300D_blue_perf.txt
Regards,