Beware of people selling so called "speed chips" that make absurd claims of 20+ horsepower gains.  These auctions just sell a small resistor that goes into your IAT (Intake Air Temperature) sensor, tricking the motor into thinking that the ambient air is actually colder than it is.  You can buy the sensor in your local electronics store for about 80 cents.  Tricking your engine into thinking that the air is colder than it actually is, just wastes gas.  You'd be very lucky to see a 1 hp gain, if anything, from using these.  Real chips costs alot more than these garbage speed chips.  Diablosport makes a Predator Power Programmer that actually reprograms your computer, and it actually works.  So does Superchips, Hypertech, etc.  These tuners cost over $300, but work.  Just like any other car part, if it sounds too good to be true (and is cheap), 9.9 times out of 10, it is.  When it comes to performance, you have to pay to play, and if you use an inferior or cheap performance product, it isn't going to do anything to help.  Don't be fooled.  Look up "chip" under car and truck parts, and tons of these things will pop up.  Total garbage.  All in all, be safe, have fun, and be legal.

Update:  I thought that 20 horsepower claims were absurd, now I see some sellers claiming gains of 55 plus horsepower.  Unbelievable.