Major loss of power - 2000 MPV
 

My wife's 2000 MPV (2.5 liter 6 cylinder) has about 115,000 miles. Recently it started to loose power such that the car would buck when going up steep hills. Yesterday, the condition significantly deteriorated over a twenty mile drive such that the car did not have enough power to drive up even a moderate incline. If I stopped for a few minutes and simply let the car idle, I was able to resume somewhat more normal driving for a a few minutes. The car stalled once, but I waited a minute and it restarted without problem and also seemed to have at least somewhat more power. Can anyone suggest the diagnosis? Thank you / Steve