VandykeT/A

A friend of mine has a 97 Z28. Since he got the car he deleted the egr, air, a/c, and put headers on it. Well after all of that the ses light never came on which we thought was odd but never really looked into. Well here recently the car has started cutting out between 3500-4k. If you floor it its fine, at light throttle its fine, its only when say your setting up to pass a car on two lane road. The weird thing is we checked the codes and found a dozen codes so some one had removed the led over time. Well it threw a maf and iat code so we tried to address that first. We took my maf and iat sensor from my LS1 car and it done the same thing. Still cutting out but another weird thing is the codes wouldn't clear. I used a diablosport programmer for a LS car, it read the codes fine and said faults cleared but when you go back in the codes are still there. What could be the deal, my programmer won't clear codes for anything other than what its made for or is it a problem with the car? We're thinking the codes have been there from little mishaps before like starting the car with it accidently unplugged etc and just haven't been removed. The codes were P0100,P0113,P0125,P0403,P0412, P0441,P1111,P1642,P1641 and all the 02 sensor codes which I know why they're there. Thanks