Date registered: Jan 2013
Vehicle: 90 350SDL, 98 S420, 97 SL500, 94 S420, past owner of W108/W112/W114/W123/W124/W126/W140 & W220 cars
Location: Tampa, FL
Mentioned: 8 Post(s)
Quoted: 604 Post(s)
Leave the snake oil on the shelf for the next guy.
I would only recommend something like SeaFoam for an engine that's got serious top end issues, and only as a last resort. It's unlikely that your engine has much carbon in it, and if it does, it's on the tops of the pistons and that's about it. A bottle of SeaFoam is NOT going to get rid of it.
I would get it limping along enough to get it back to Miami and let your MB guy have at it. Someone who knows this engine and carbs will know where to start, and by taking it a step at a time can get it back to proper running condition.
A lot of what you are probably suffering from is probably a collective amount of little things that as a group are making it run poorly. Just about everything that's been mentioned in the thread up to this point is simple and requires minimal cost to resolve.
Tough it out, use the tranny to kill it if the dieseling is excessive, and get it to someone who is qualified to sort it out. I can remember picking up a 1970 250C at an abandoned property auction in Orlando back in the 90s that sounded very similar to yours. I got it home, spent a few days getting everything adjusted properly, and the car ran like new.