I'm sitting here wondering about the "rust" theory. Sounds like you need to hook up with Cap'n and the trials/tribulations of his 300E. I want to think the Bosch system on your car is probably doing what it is designed to do, you just haven't put your finger on what is causing it yet. Have you tested the various sensors, etc.. that this car has? How far in the fuel distributor did you look? I would not advise looking too far into it. Cap'n showed me what is in one and it ain't pretty for the diy'er.
This is the first time I have ever heard the theory that because the plugs are red there is rust in the fuel system - hmmmmmm (but keep in mind I mostly mess with the diesels
) - I'm going to have to think about that one for awhile. Are you sure it ain't running lean? Can you get a duty cycle reading? If it is on the higher side of 50% then it is lean and can cause you some runnability problems.