before you go replacing anything or going worst case scenario, just go under the hood and really push the sensor plug in firmly. this is a known problem and one that i had when i first bought my VX. it will also do it sometimes after washing the engine bay (gets knocked loose) and when it's really hot. This thing is very sensitive, but everytime mine has had trouble that has been it. tone told me about it on my second day owning my VX. do a search for MAS or Mass..

hope that is it, it would be expensive to replace it. but if that isn't it then more than likely it is the intake manifold as others have said.

hope that was helpful
technocoy.