Hey guys, this sounds like a faulty air flow meter. A few solutions-
1) replace the thing (a few hundred bucks!) or 2) carefully remove the
black plastic top (this is not trivial to do- take your time and don't
break it!) and then clean the contacts inside. You can spray them with
electronic cleaner or you could reposition the wiper arm to a new spot or
best off doing both.
Cheers!

Matthew Pollard             http://www.uidaho.edu/~poll7356
Dept. of Chemistry               http://www.chem.uidaho.edu
University of Idaho                   http://www.uidaho.edu