There might be a short in the wiring harness for the throttle postion sensor.
If there was a short in any other sensor or harness which ran off the same supply as the TP sensor (such as the oxygen sensor or coolant temp sensor), it could pull the supply voltage for the TP sensor down; which would produce that code.
If your engine has been modified, or you have added any aftermarket performance parts, then they could cause a problem of this sort.
If the electronic spark timing control system was bad, it could also do this.
If that is not the case, then I would check to see if the EGR valve is sticking open.
If all those items are good, I would replace the spark plugs and plug wires.
And if it still runs badly, I would bring the MAP sensor in to a parts store that can check it, and see if it has a problem.
I hope this helps!!!