I recently bought a 2002 F350 powerstroke crew cab with 165,xxx miles. The truck is in really good shape for the year, all I have done is change the cab lights and put wheels and tires on. Truck rides on 35s with 20x10s.....not long after buying the truck the check engine light came on, it would come on and go off and so fourth, never would stay on long. I took it to a friend who owns a semi truck buisness and shop. He hooked it up to his scanner and pulled 3 codes (at moment I cannot remember codes) he was able to clear 2 but was not able to get into the 3rd, called the program that his scanner is through and they said if it has a tune on it that it wont pull it up. I dont know if the truck was tuned, the previous owner does not either, there is no switches, monitors or anything, but the pcm has been removed at some point, truck does not run like stock.......so I never noticed a difference when the light came on until recently, the passenger side exhaust manifold gasket is torn so I have the exhaust leak sound when I give fuel, i now notice when the light comes on the exhaust leak noise stops as if air wasnt going through there. Any clues as to why the noise would stop?