Mell, I recently posted a thread on my particular problem which part of, was the symptoms which you have posted, drives about as per normal on small throttle openings, then when you put your foot down the car revs up but no drive (as neutral). I bought a cheap MAF unit off Ebay for around £38 delivered, to try and it sorted the car. May not be the solution to your particular problem, but for the cost and the option of having a spare MAF to try when these type of problem arise, all for a 10min job to change!!