Performance chips

So I've done some research into computer chip upgrades for performance enhancement, and am wondering if anyone else has used them and if they produced any noticeable differences? If so, which is reccomended and why?

[sleepyalero]

they aren't worth it... they don't really work. Ebay... fake.. most others are fake too

[Valley olds]

Nope. Not good. A good tune for the vehicle would be with HP tuners, it is kind of expensive though, and if you dont know what you are doing, you can really mess up the engine.