You get em from aaronneon. They clamp the MAP sensor so that it only sees a certain amount of voltage so that the car adds less fuel and it also makes the car pull less timing. You use it in conjunction with a dyno that checks A/f ratio and you set your a/f ratio with it. Can be bad if you set it wrong cause by making the car run lean then it goes BOOM! By setting it properly many people have seen nice gains on the dyno.