man it's amazing how many people have had that same problem with a dirty MAF sensor causing poor performance. Judging by how many people just in this forum alone have touched on the subject (including me), it is something that mechanics give little thought to but really needs to be paid attention to. I'd run some injector/fuel system cleaner in there, check the MAF one more time, clean that throttle body, and check the spark plugs, cause besides that, not too much else can go wrong without causing a code to be thrown at you.
Also, just as a side note, I'm beginning to wonder if having a K&N is what fouls these MAFs up with the oil they may make the intake ingest (possibly because of a supercharger sucking the air in?), and the extra dust that may be let in through the pinholes in the cotton weave. I cleaned my MAF and then checked it again two months later and it was dirty again! Maybe the K&N is the culprit in some of these MAF cases....