Got this installed on my 2006 coupe after the intake, plenum spacer, headers, and straight test pipes into the stock catback. Car is a different ride! The power is nicely linear and I picked up 4mpg compared to my untuned ecru with the mods. Higher redline, no 0-60 training wheels, and all smiles here.
I think its over priced...
I had to have the GT for awhile cause I wanted to see how many miles I got to the tank once I filled the tank and runned it all the way to empty. I do like the grading while I am driving, as far as preformance since I am not gonna pay to get it dyno checked for increased HP if there was any I honestly didnt feel any increase when I changed it to stock to premium on the GT setup. Also those who get it for the G35 its much eaiser to install using the fusebox under the driver side instead of the engine fusebox. I would return it but I bought it when there was a sales going on so I'll keep it, would recommend the borla exhaust system pricey but sooooo awesome I feel those HP's!!!
Hypertech for my 06 g35x
After installing the disk set-up which was quick, the steps to download current information was really simple. Then the hook-up to the car and following instructions was as straight forward and as easy as the web site explains. The results will not overwhelm you, but are noticeable. My car was slightly quicker (1st and 2nd gear) and gear transitions a little smoother. Can't say I noticed an improvement in gas mileage just yet. Lastly, I unlocked the top speed which allowed my car to get to higher speeds with significantly less effort. Overall, I was pleased with the results. Next up, air intake maybe?