Ive been lookin around for awhile now and i keep seeing these tunning things. can some one tell me what they do? All of them say they can improve my performance , is it worth it?

 

They are called handheld tuners and they plug into your ecu which allows you to remap, or reset, the stock parameters of your car. Depending on your year and the tuner brand you can eliminate your rev limitator, reset your top speed limitator, if you have an auto, reset your shift points so that the car shifts where you want/need it to, increase shift pressure (makes the car shift harder which improves shift time and tranny life), advance or retard your spark advance (this is a hp maker), reset your air to fuel mixture to maximize power (only let a shop do this as you need a air to fuel monitering device to do this properly), reset your gear setting for larger gear ratios if you do a gear swap, reset your rim size settings so that your speedo stays on, and they do a handfull of other things too.