I have a 1988 300 SEL that I have been having some trouble with and need some help.
The problem is the engine quiting. It is intermittent, and gives little or no warning. Usually does it when coming to a stop during braking, or when decelerating, but will also do it at any time. It always starts good when cold, but on a hot start it will crank good run for a second or so and then the engine will start running rough with the RPM's droping untill it quits. When restarted, it runs ok most of the time. Sometimes have to start it a few times before it will run. If I try to rev it when it is about to quit (less than500 rpm's) it will sometimes smooth out and run fine at its normal RPM.
During acceleration, it will start out pulling like it should, but sometimes will die down, and not be able to accelerate up to speed. During this, there is usually a slight drop in rpm's and the economy gauge (I assume hooked to vacuum) will peg out. The engine will still be running and running smooth, but just will not take the throttle input. The engine will either run like this for a while and quit or start operating like it should.
I generally do all the work on my cars myself. However I knew that I didn't know enough about it to fix it so I have taken it to several shops that were not able to find the problem. I feel that this is because of the intermittent nature of it. However even when it has quit while being driven into the service bay the problem could not be found.
Below are some things that I have done.

First of all I rebuilt the engine. I'm in the auto machine shop bussiness. It mainly needed a set of valve guides, and other head work, but I went ahead and rebuilt the engine to be sure.

I replaced all the fuel injectors with new ones from Mercedes.

I replaced a cracked rubber boot or duct that goes from the fuel injection unit to the intake manifold.

I replaced the fuel filter.

I checked the fuel pressure (3 Bar)

And it held this pressure for 30 minutes. I was told that this needed to be checked by a local mechanic so I borowed the gauge and checked it.

I'm open to any suggestions.

I like this car and would like to be able to drive it without being woried.

Thanks

Bill