I just purchased a 1993 400E, and In doing the shakedown, changing fluids and filters, etc. I noticed that the left air cleaner mount next to the firewall is missing! In it's place the hole is filled with a black sealant of some kind. Before I start screwing around I'd like to know what lies beneath this mounting hole. Can I helicoil the hole and replace the mounting stud without major bad things dropping into the engine? I don't want to start something I can't easily repair without major disassembly. If this is a solid casting I'll just helicoil and be on my way. If not, what is involved in fixing this so that both sides of the air cleaner plenum assembly are tied to the car? The only thing holding the air box in place is the two wimpy clips up front and the studs the U shaped mounts slide into in the rear. That being said, I LOVE THIS CAR! 124 forever!