This is a 2002 Safari AWD.
Back in June the Service Engine Soon Light came on when accelerating from a right turn onto a main Highway. Before the light came on, the van would not shift into 4th gear on the hard acceleration, only heard engine rev going up without speed changing or shift to next gear, then Engine Service Soon light came on. The dealer changed the Mass Air Flow Sensor (covered by ext warranty) and I had them change the plugs wires cap and rotor, flush the radiator and change the trany fluid ($1100 later). Now I still experience Sluggish acceleration (Engine delivers limited power under load or at high speed. Won't accelerate as fast as normal. Loses too much speed going up hills) the MAF has been change again with still no change; I was given a gas filter to change, (fuel pump sounds ok) still no change. It's at the dealer again with a MAF code and the tech experienced the Sluggish acceleration, but doesn't know what is causing the MAF code. 
Does anyone know what is going on? It's been at the dealer for the fourth time and has been there for two days. Now they tell me I will have to pay for Diagnostic time. what happened to Mr GoodWrench! Mine needs help.