Help troubleshooting "sound package" drain on 996 C4S

Hi folks, The battery on my 2004 996 C4S cab has been draining in a couple of days so I've been going through the process of finding the cause which was a 200-300 mA draw after being off for >1 hour. It drops to the expected ~25 mA when I pull the D9 fuse which is labelled "soung package" in the fuse list (not a typo). Not being super familiar with the car, having to take youtube lessons on how to use a multimeter to measure current and the alarm going off all the time has been a fun challenge (I've disconnected the alarm horn and siren). I have the PCM2 double DIN nav unit, Bose labelled speakers in the doors, an amp under the false floor in the trunk mounted to the left of the spare wheel and a CDC4 CD changer. Roughly around the time I started to have issues the Nav stopped working with an error message specifically about the nav ("System error: Navigation System not available") when starting the car, which I could clear to listen to music without an issue. Once it started without the message and the nav worked, but only once, so it working is the exception to the rule. I should also say that I've just had the engine rebuilt, so while most of the work was at the other end of the car, it's possible it could have disturbed something. While looking at the CD changer connections I noticed it was fiber optic so did some research and found many Rennlist and other forum posts about MOST etc so I understand there is a loop. I've pulled power to the amp and the CD changer and no change to the draw. Hoping to get some pointers on possible causes and locations of issues as I continue to work my way through. 1. Are there other components on the D9 circuit other than the amp and CD changer that draw power? I'm wondering if the NAV issues might point to a problem in some NAV specific hardware. The PCM2 head unit itself seems to be on a different circuit. The sub in the passenger footwell I assume is passive and powered from the amp. 2. With MOST, is there anything I need to be aware of? It seems like any device the optics flow through need to be powered as when I pulled the amp power the PCM2 gave an error message that said all features were unavailable which seems to be most related. Many, many thanks!

So I am now focussed on the apparent navigation module that's included in this package. Found this thread about an older Cayenne, that lead to a failed navigation control unit - 99664220502. Thread: https://rennlist.com/forums/cayenne-...available.html Part: http://www.autoatlanta.com/porsche-p...=99664220502#a It's listed under one of the PCM2 options on page 578 (diagram) and page 579 (list of parts) here but it doesn't show where the unit is located : https://www.porsche.com/all/media/pd...96_KATALOG.pdf Anyone know where this is mounted? Possibly behind the PCM2? I'm also going to check the mobile phone module that I've learned is under the drivers seat as I can see what appear to be a MOST loop going to it.

Just following up - it is mounted in the back of the PCM2. It slots in without screws. I also learned via Renntech that the part is also available under some exchange program - 996642205X - but no idea how that works. Photos.

Just to close the loops, removing this module removed the drain of around 300mA, so the car now pulls a normal 30mA when off. I get the same error with it out and in, but at least the battery isn't draining in a couple of days. It's not worth it to me to replace at quoted prices (new or used) unless a "for spares" PCM2 comes up at a reasonable price that I can extract the module from.