Try cleaning you MAF sensor first (as stated above). Then if that doesn't work, you can get an OEM Bosch sensor for around $180.

Pelican has the Bosch sensor for around $225.
Autohausaz.com has the Bosch for $180.

Don't bother with those ebay MAFs. They are poorly refurbished by people who don't know what they are doing. I went through two of them and they had really poor performance. waste of time and poor customer service.