excessive81

i am trying to help my friend with his mustang. he has a 2003 gt with a vortech blower. he has a miss at idel and at a steady cruise...have not witness that part. he has a piggy back computer with all the gooies(wideband, data logging ect) but i don't see this being in the tune. he has taken it to several places but with all the stuff he done to it they all just guessing. he has replaced plug, coils, mass air meter and even the computer as some one guessed that to be it. it is a sweet car and he so pissed he almost over it. he been chasing it for almost a year. car runs fine at wide open throttle or just driving around. i new to these so i don't know where to begin. i have a blown corvette and have tons of gm knowledge but mustangs..well i just picked up there parts for my buissness so i am going to start learning so we can work on them to