possible hego but they usually neva cause pinking, wudnt thought it being the maf mate. im a tech at a ford dealer n neva had maf probs. had problems with the main injector multi plug (n/s inner wing) they get damp and cause funny symptoms. mite b worth checking that. u checked fuel pressure and changed your fuel filter? could b fuel pressure related, that would cause the hego to run lean and think its faulty, cyl 1 furthest on fuel rail so wud get the lowest pressure. fuel pressure wont give a fault code