Ground issue on 2003 Mustang GT?

[2K2 LS1]

I hear a buzz through the speakers when the radio is on. The battery goes dead after the car sits any longer than 48 hours. The car sometimes will be less than 11 volts on the battery level indicator gauge, but once I give it gas it jumps to 13 volts and charging. I put a meter on the battery terminals when the engine is running and get consistent 13 volts. The battery was pulled and tested-results ok, the alternator was pulled and tested-results ok. Where do I go next? Where are all the grounding point on this car?

[Trick Pony]

If the battery is dying when the car sits then you have something causing a parasitic current draw. You can disconnect the positive cable from the battery and put your meter in line to measure current. Not sure what normal would be for your car as it will vary by vehicle and I know newer cars pull more current sitting than older ones but maybe someone could chime in with that. If you see any kind of significant draw then you need to start pulling fuses one at a time.
Keep in mind that if you have a serious short then this test could blow the fuse in your meter or damage the meter itself. You can check for a short by pulling both cables off the battery and measuring the resistance across them. If the reading is close to 0 then you have a major short.

[2K2 LS1]

Looks like me and the Fluke will be busy this weekend.

Off the wall guess; but can a radio that has a jammed cd player, draw enough to cause something like this?