I saw a message on this board regarding an install to a 99 M3 which said there
are jumpers inside the empeg which change between 4V and 1V. The problem is
I cannot find the message on the board no more so perhaps you need to check
with empeg if this is true. Also note that if you take the unit apart you void
the warranty so you may need to send it to empeg.

Hope this helps,

Dan