Thanks to everyone who offerred their opinions and direct knowledge of my problem! I picked up my car from the dealer yesterday and voiced my concerns (even quoting some of you responders) about the fuel recommendation. This is the only Mercedes dealership in town and I have been extremely satisfied with every department I have dealt with there so far. The service manager is a 20 year veteran at that dealership, a very friendly person and seems to genuinely know what he is talking about. However, he reiterated that MB has told his shop foreman that in certain, isolated cases (where there is carbon buildup on the #4 injector) better results and less buildup can be gained from 87 octane fuel. He says he has had a few cases like mine in the past and this took care of the problem.

He went to the foreman to see if a service bulletin existed that spelled this out, but couldn't find one. He said he knows the instruction was given verbally by phone from MB to his shop foreman. He said I was free to use any fuel I chose, but that he recommended trying the 87 octane fuel. What was done to my car:

Code 8319 Faulty injectors. Performed short test. Performed ME-SFI flash and scn code fuel computer. Replaced all injectors. Replaced ignition coil. Replaced spark plugs. Drained fuel tank, clean air intake system, add BG44K fuel additive to fuel tank.

All work was performed under warranty. Ignition coil was part of the prescribed remedy from MB--service manager didn't feel it was necessary, but followed MB's procedures. Also, injectors were not exact replacements of the stock injectors as the new ones were some sort of upgraded injector. I spoke with a representative from MBUSA's Customer Assurance Center today and told him my story. He was unable to find any written material to support using a lower than 91 octane fuel in this car, nor had he ever heard of such a remedy. He recommended that I continue to follow the fuel guidelines in the owner's manual, so I will. It was suggested to me on one of the forums I posted this issue on to rotate brands of fuel periodically so that I don't always have the same additives in every tankfull and I will try that as well.

Thanks again to everyone who responded to my thread--I really appreciate your collective knowledge!

__________________
--Craig.

"When you see a fork in the road, take it!"
(Yogi Berra)