This is my first post so bear with me.
I just bought a 2002 WRX 130xxx miles w/ AEM Intake & HKS Exhaust. (from an old lady, how awesome is that)
After a few days & a few hundred miles my car decided not to start anymore. It sounded like the starter was not completely engaging the flywheel I would just hear the starter spin and occasionally grind on the flywheel but never crank the motor. So obviously panic set in, I did a lot of forum surfing and found a couple possibilites 1. starter needs to be regressed 2. the starter solenoid is not working properly and needs to be replaced or 3. the flywheel/starter has damaged teeth and needs to be replaced.
I decided I would pull out the starter check to see if there was any noticeable damage. So I found http://www.wrxtra.com/Documentation/doc-1002.pdf good instructions on pulling off the intercooler except for one part where it says stand on the drivers side and wiggle it out but I found it was easier on the passenger side using a 3/8 socket extension to push on the tab on the turbo-to-intercooler hose with one hand and while wiggling it off with the other. I spent 20-30 minutes trying to pull it off from drivers side and 2 minutes to actually remove it from passenger side. After I finally got the intercooler out I went to take off the starter and noticed it was loose! I've never been so happy I tightened it up put the intercooler back in and BAM worked great.
In conclusion if your experiencing this problem spend the hour and check to see if its tight, free and easy fix.