An old thread but thought I would just throw this in ---

After getting the *(& scared out of me the first time I turned off my Jeep after installing the empeg, I asked rob for one of the plug-in diodes to see if it would solve the problem. I've had three head units in with the same setup and never once had a problem.
However, received the plug-in cable yesterday and have to say that everything works perfectly now! No thump, properly sleeps and wakes up, etc. etc.
So those having this problem I would definatly ask Rob for the cable and you should be set!