I have had this problem a few months. Quite often the car behaves as if I am in too high a gear. The revs appear fine but there appears to be no power on hills and I find myself crawling up even the slightest incline in 2nd Gear. Yesterday, I was stopped by some traffic lights at some road works (on a slight hill) and barely managed to pull away in 1st gear. I crawled to the top and once the road levelled off, I was able to move up through the gears and things seemed to return to normal.