Leaning out!

so my stang's been leaning out on me at full throttle, about 3000 rpm. i thought the ignition was cutting out, because it would just stop running all of a sudden. i was instinctively lifting when this happened, but i finally stayed in it, and it was popping through the exhaust like mad. i'm going to check the fuel pump circuit... it can't be the pump itself, i just replaced it with a bbk 190lph... i doubt it's the regulator, it's also a new aftermarket piece.

it also runs lean at low rpm at partial throttle. i thought it was because of the mods i've made, and the computer couldn't keep up.... but that makes no sense, the changes arent' that drastic.

i'm going to start backprobing all the sensors next time i have a free day to see if one's not getting the signal through. i suspect the driver's side 02 sensor, the passenger side one is relatively new.

any thoughts?

mods to the engine are bbk cold air, 73mm calibrated maf, 24# injectors, underdrives, larger alternator, 180 stat, no smog pump, EGR eliminator plate (3/8" thick), full-length headers, no cats. i don't have a chip or anything at this point.