Smooth Idle, but crappy power, crappy acceleration

Erratic behavior when throttle is open more than 15-20% The other night, I was driving and the car started to lose power and run pretty crappy (erratically) when ever I was accelerating or holding a certain speed.

The CEL is intermittent and is usually off by the time I get to the 1 mechanic in the area with an OBD1 scanner. In the past when it has done this I would clean out the egr valve and/or the MAF sensor and then it would be fine. This time I've done that 3 times, changed the fuel filter (which was pretty dirty), cleaned the throttle body, checked for vacuum leaks, checked spark strength, and still haven't found an answer. I think the problem is in the MAF sensor. I know how to hook up my multimeter to it, I just don't know what the range of the signal voltage should be.

As of today, it's ranging from 2.59 down to 2.56 with nearly wide open throttle. Again, this crappy running with throttle open is only when the car is in gear. Does anyone know what the signal voltage should be or have any other ideas?