P0641

P0641 has been the common denominator of the recent issues of my '07 Cobalt with 2.2 L EcoTec engine. A year ago, it came up with an engine reduced power over the display and a P0641 code and the camshaft position sensor code. I replace the sensor and it still happened. Then I took it to a GM dealer they said it was the ECM and replaced it. Less then a year later I'm having the same issue. I didn't have time to mess with it and I'm not that great with all this new electrical stuf, f so I took it back. They ran a bunch of diagnostics checked for five volts at all the sensors on that circuit and they all seamed good. They told me it must be a sensor and we began the process of eliminating a few of the possibilities of which sensors by unplugging them one at a time to see if the code would reappear. We have it narrowed down to the MAP Sensor and the Accelerator Pedal Position Sensor. I replaced the MAP Sensor and it is still doing it. I'm about to buy the APP Sensor to see if that does it, if not I'm going to be lost. I'm just looking for some insight and to see if anyone else has had this issue because apparently my local GM Dealer can't figure it out.