Hey Dude !
I have had my Diablo in my car since I bought it. I love it. I did notice a pretty big difference. It will take care of those gears (speedo calibration), it will also take that engine light off and it will also advance your timming to about 15 or 16 degrees. I like this chip because you don't need to buy the box for the speedo clibration and you don't need to buy the MIL for the H-Pipe and you don't need to buy the Steeda Timming Adjuster because the chip does it all. When you get the Supercharger you can get Diablo to program it just the way you want it. The chip can be re-programmed custom to your needs. NOS, BOOST whatever.
I've got nothing but good things to say about that chip.
Last year before putting my stang in storage, I took the chip out.
When I took my stang out this year, I drove it a while before putting the chip back on. WHen I did put the chip back on, I did notice a big diffrence in throtlle response, and Top End gains.
Let me know if you have any questions !
I bought mine at
http://www.need-4-speed.com