anybody tried a performance chip in their car? i'm a jaguar novice here and even a bit of a "new" car novice considering the car the VDP is replacing is an 89 mercedes, but the idea of more HP and MPG is appealing.

my question is can a chip really deliver more power and mpg all in one? they claim all you have to do is plug it in to the IAT sensor and thats it. wouldn't jaguar have made their car as efficient and powerful as they could have from the start? JAGUAR XJ8 G-Force Peformance Chip