I See from many of you guys' car mods that you have either Diablo or JET. But then from reading from some posts I hear that they actually dont work for anything. Any opinions

Don't get either one.

Go for the SCT Excal2. It's loaded with all the options you could possibly need, 3 banks for seperate tunes, and a TON of shops support it with their Dyno's/software.

safe your self time and just hit your car with a hammer you will be just as pissed after either way.