MBDOC is probably right. The "warm up regulator" or I call it "control pressure regulator" is the most common problem on these cars. (Ask me how I know. I have one). You really need a special fuel pressure guage to check the control pressure when cold and when warm. As the car warms up, the control pressure goes up which leans the mixture. One thing you can check, make sure the control pressure regulator has power and ground at the plug when the engine is running. If not, you will have the problem you have. I believe it also has a screen filter in one of the fuel line connections. You could try blowing air thru it in both directions and see if anything comes out. I really don't think you have a fuel dist problem.

Good luck
Paul

__________________
84 500 SEL (307,xxx miles)