My first guess is TPS, my second would be a MAF issue. The MAF would usually shoot a code, but with the TPS, it's hard for the ECU to detect it unless it is completly open or shorted. Do a sweep, read the signal voltage, it should be right under 1V (.9xx) and as you open the throttle there should be a smooth increase in voltage until about 4.3-4.5V at WOT. Any spikes or dips will tell you that there is a problem. MAF's will do all kinds of crap if just a little dirt gets on the sensor wires.