I have a '91 300E with 63K miles on it. No adjustments have ever been made to the CIS system or any other system. The car has always been treated with TLC and the only thing that's ever been installed that didn't have an MB part number on it is Mobil 1 in the entire drive train.
This summer I began having problems trying to start the car when the weather was hot. Now it's cooled off and the car starts, dies and easily restarts. Once started, it runs like new.
Perhaps there is some part that is going south but I'm wondering if it isn't just an accumulation of individual things that by themselves wouldn't be a problem but when added up, create driveability problems.