Peter,
Sorry to hear about your difficulties with that car. Perhaps my suggestion of trading the 300E for something quicker has even more merit? I'm not saying you did anything wrong with installation, but if the issue were to go to court or otherwise get nasty it would help your case if they were "professionally installed". Even if you and your friend were more competant than the "professional" installing them. Good luck with getting it resolved. Glad we could help.

Lee