Here's a question for ya:

My '82 245 idles pretty rough. While I haven't done a recent, thorough check of the fuel system, in the last year I have cleaned and checked the flow of the injectors, and I do believe the fuel delivery system is pretty much OK.

The last time I had the intake manifold off, by peering into the head I could see that a lot of black junk had built up on the stems of the intake valves. I have come to believe that maybe this junk is interfering with a well-distributed flow of the air/fuel mixture into the cylinders. (As far as a possible cause, the car has been running rich, and may have been running rich for some time.) This must be the problem that fuel "detergents" in gas and fuel system cleaners are intended to counteract. It also occurs to me that this problem may be peculiar to the continuous nature of the fuel flow through the injectors in the CI injection system.

What I'm thinking is this: Next time I have the intake manifold off, why don't I reach in there and clean that stuff off of there? I know I would have to be very careful of the valves, and very careful to get all that stuff out and away from the rest of the engine. Would you suppose that that stuff is brittle and removeable with a little gentle scraping, or would you suppose that that stuff is stuck on there like concrete sticks to rebar? Maybe it could be cleaned off with a little gentle scraping and a little local application of fuel-system cleaner. Maybe a long Q-tip soaked in Berryman's B-12 (a solvent)?

Thanks in advance for your suggestions and advice!