Originally Posted by 4EST
I routed the wire from the radio to the roof light. I removed the rubber from the door frame, and this gave me access to the A pillar (there is about 6-7mm of open space covered by the rubber door seal). Take care with the airbag, the wire must not block airbag deployment. I removed the sun visor and roof handle and I could lower the roof a bit and push the wire all the way to the center front dome light
Thanks for the further details! I'll try to follow your instructions to install the mic on my e91.