Issue with radio (CDR-220 or amp?)...

[rrappel]

Just bought a 2001 Boxster and having issues with the CDR-220 radio. The right channel level is much lower than the left (at least listening to the speakers on the dashboard). Everything was working just fine yesterday; popped in a CD this morning, started up the car, and noticed the lower volume.

Not sure if the issue is with the amp, wiring, head unit, or speaker. I did a little googling and couldn't find any type of schematic which might help me narrow down the problem. I believe the amp is in the front trunk, behind the spare. Does anyone have any suggestions where to start (or even where I might be able to find a schematic)?

Thanks,
Ron