Originally Posted by Kev

I have done extensive dyno work on these XT660's, the most HP you would see by just adding a Power Commander is around 2 to 2.5 HP & that is with a fully mapped custom made fuel map.

A fuelling device is used to correct the A/F ratio, it is not a HP mod, it offers the least HP gain of all the mods by it's self. Add a fuelling device to the combination of other mods & you will see big HP gains, a fuelling device corrects the A/F ratio to get the most HP out of all the added mods.

In the past we have discussed the differences between the Nitro X & the Kev Fuel Mod, here is one of the past Posts.

http://www.xt660.com/showthread.php?t=12426&highlight=nitro&page=2