i read all the posts about a smoke switch and had to try it. i jumpered the C and D wires on the MAP sensor of my "bone stock" 04 CR Cummins(555 not 600) and i got the CEL(check engine light), but no extra smoke. it went to about 10 psi boost and stopped, like it had a governor on it and i realized, hey, it does. for all parties interested in this next little blurb, please feel free to read on, if not thank you for your time so far.(not being sarcastic, seriously) so, what happens with a stock ECM is that when you manually change the boost(turbo) pressure, the computer only has one way to regulate itself and that is with fuel. so what it does is defuel the truck so the engine can't speed up(without fuel it doesn't matter how much air you have, you ain't goin nowhere) therefor the exhaust gas does not spool the turbo up, thus regulating your engine and not giving you power. i found this out another way which will also backup my theory. i have a boost elbow on my stock turbo, and when i lock the set screw all the way down to turn up the boost, it does identically the same thing, only it will let you go faster, because the sensor will read actual boost level and there is some fudge factor in the stock ECM. i turned the boost bck down to about 24-26 psi and the truck runs like a spotted ape. i hope this info was of some help to anyone inquiring about a smoke switch and to anyone that reads this and believe i am wrong or notices that i did something wrong in the process, please reply. i DO NOT get offended by constructive critisism, that is what forums are for. to share your experiences and learn for other peoples mistakes as well as your own. also keep in mind that this thread is about a STOCK truck only. i have no idea about doing this on a truck with a chip installed. thank you for your time and i hope you're still awake after reading this novel.....