I have a 99 Forester with 160,000 miles on it. Started to notice several weeks ago that while up to speed (25 or 65 mph) and at a steady pace (2,000 rpm range) a slight hesitation. Not enough that the rpms drop or become erratic on tach. Slight but noticeable, at least to me but happening more frequently. During idle and under acceleration it is fine. As said only during up to speed and at steady acceleration, does seem to be effected by more or less strain due to starting up a incline or going down a incline but with foot still steady on the pedal.