Tools you will need:
Security Torx Screwdriver set
Multimeter (I used Techshop's Rigol DM3058 Multimeter, but a handheld will work just fine).
Mass Air Flow Cleaner (available at your local autoparts store)
The Mass Air Flow Sensor sits within your cars air hose and lets the cars computer know how much air is flowing into the engine. This allows the computer to adjust to achieve an appropriate ratio of air and fuel (and spark) in a fuel injection engine.
On a 1999 Subaru Forester, the MAF Sensor is located on the passenger side, on the air hose that comes off of the air filter. The one in the picture below has a blue stripe on the top.
Step 1: Open Air Filter Cover
2) Lift up on the cover.