The hard starting when the car is cold could be that your cold start injector is not working or your coolant temp sensor is not up to snuff. The car runs without computer in it so once it is warmed up shut it off take the computer off and start it up see if anything changes. You can also check the coolant temp sensor by measuring its resistance. Get the shop manual or the CD, it states the correct resistance values for the coolant temperature. It may also be that car is running in "limp" mode because of some sensor problem. Have it checked out by Benz, however be warned that as soon as they encounter some problem they may not go any further until that problem is fixed. Also the 86 300E have a little adjusting screw for the fuel mixture, it is in that little hole through the airfilter housing, but should not be tempered with without a lambda meter hooked up to the car. Find a competent Benz pro in your area (does not have to be the dealership) and have him look it over. Your average mechanic can and will do more harm then good when it comes to diagnostics.