Hello,

It really sounds like you could have a fault in your air-mass meter. (I had an identical problem to yours a few weeks back... after I cleaned the air-mass meter completely, it ran fine with no more problems).

Try cleaning and re-seating the electrical connectors on the air-mass meter. I used a small wire brush to clean off all the corrosion that had accumulated on the contacts.

If that doesn't work, try taking the entire air-intake "hose" assembly apart (up to the throttle plate), and cleaning out any dust, debris, oil, etc.

Hope that helps!