Brother of the Benz, Shyne
Over the years I haven't been much for snakeoil remmodies, but in the case it sounds appealing.
My 1987 300E is nasty there too!
I believe the spray can for cleaning the intake plenum, sprayed while the engine is running.
Then possibly the liquid can for pouring in the intake to gain application to the cold side of the intake valves. Finally drowning the engine with the cleaner.
I believe you let it soak for a time; then start it to remove the cleaner and any carbon that has been softened.
Worth a try and cheap!
Happy Trails Beep Beep from The Spiderman in Houston!!!