Well, since unplugging the MAF actually improves the situation, I'd say a dirty/malfunctioning MAF would be the top of the culprit list.
Take the MAF off, spray some electronics (or brake) cleaner on the two little elements inside the MAF (don't take it apart), remove the negative battery cable for a minute or two, and see if the situation improves when you put it all back together. Best to pull the battery cable before removing the MAF and put it back on last.
You could also try spraying the connectors (both MAF and harness) with some electronics cleaner. Maybe the contacts are dirty/corroded.
For the cost of a can of spray cleaner, it's worth a try.
