cylinder bank 1-4 cutting out.... help..

ok... the car is all apart right now for 30K service and heads. And I'd like to solve this problem if possible to replace the bad component etc while its down...

While I was driving it the 1-4 bank would often intermittently cut out, when driving or idling and sometimes just for a second, sometimes 30 seconds off and then come back on, sometimes it would cut out and not come back, until cooled down and started the next day. sometimes it doesn't do it at all. but when it does it and you shut it off, and start it back up it will always at least start up on all 8 then **** off quickly after. when this has happened I have checked the following..... It is getting spark, it is getting fuel... from what I can tell, I have tried swooping both coil packs etc. from either side, I know its getting signal because I can pull a plug wire off and it arks, I think its getting fuel pressure but can't be sure if its getting enough. because I have checked the thing on top of the filter to see.. So whats left? fuel injection problems??? My mechanic suggested air flow meter.. what do you think??

Thanks