Massive parasitic current leak in stereo/nav circuit

[Multibeemer]

As I've described in another thread, I've identified a massive parasitic current leak in the stereo/navigation system circuit in my '03 4.4i. When I remove the fourth fuse from the front in the fuse box in the right side of the luggage compartment and place the leads of my ammeter across the fuse's connectors, the current solidly pegs the needle of my ammeter on the 250 mA scale, so the leak is huge. I seem to remember reading that parasitic leaks originating from the stereo/nav system are fairly common in these cars. Is there a straightforward way to track down the source of the leak in the nav/stereo unit? I dearly hope I don't have to replace the entire unit, which is probably costs a significant percentage of the entire vehicle's value... Thanks.