So I was on ebay look at part for my V and I always see a that someone is selling a "speed chip" , so my question is has any one ever bought and use the chip ? It say it will increase horsepower and mpg
There is no such thing as a speed chip or power chip. Most things are designed to pump more fuel into the car, or like the throttle position mods, make it feel like you're driving normal rather than thrashing your car. A proper computer would give you some power if you can remap your system, usually at a very high loss of economy.
The only way to get better power is to put good headers and a decent flowing exhaust on it, then if you want, look at Cold Air Intakes (although it has been proven and tested 100% that 99.9% of the time, you lose power with them).
Your next step to bigger power after that would be bolt-on power (turbo/supercharger) or bigger internals.
These chips and mini-superchargers are rubbish my friend, steer well clear of them!
I've looked into performance chips, made from JET performance, the only thing I've found that they offer is an upgraded MAF sensor, thats recommended to change if your changing your intake. Again, cold air intakes don't really add any power unless you do other things as well, I know personally i'm looking into a short ram intake, which has a nice sound and is a bit of an upgrade from the factory intake, but no chips so far.