Actually, the first thing that came to mind while I was reading your question was the MAF. But I doubt the replacement part is bad, and in fact the original part might have been okay. Instead of re-replacing the part, make sure the contacts for the mass air flow sensor are clean. Often the problem is not that the MAF is bad, but that the sensor and the connections are dirty. CRC Industries makes a specific cleaner for the part and connections. http://www.crcindustries.com/auto/content/prod_detail.aspx?S=Y&PN=05110
Seems like you did or tested everything else, and the symptoms fit.