my 93 gt is missing out bad at rpms above 3,000 i am not a very mechanical person, but here is what i am thinking, i just did a tune up new plugs cap and rotor, the cap that i put on it was a real cheap aliminum one (it all the parts store had) coulf that cause it? or it might be my tfi mod.? or my o2 sensors are real old with 120,00 ile on them could it be those? i am leaning toward the tfi mod. but i need to know if the car will run at all if its bad, cause it does run fine un til you get it up over 3 to 4 grand. also it will do this in nuetral too. hope this all made sense, any help you could give would be greatly appreiacted, because i cant stand to drive a stang that runs like crap!