Vintage Cars: 1985 mercedes 500SEL, mercedes 500 sel, bosch platinum

Question
I have a 1985 Mercedes 500 SEL. I bought this car in April from a private party that hadn't driven it for a year. It ran good until about 3 weeks ago. The car ran very rough, and shut down when the accelerator was pushed. I had someone do a tuneup with new Bosch platinum plugs, a new rotor and distr. cap. It still wouldn't run easily. I kept letting it idle (very roughly) and again it would shut down whenever the accelerator was depressed. The mechanic that did the tuneup said that possibly it had built up gunk on the injectors, so I put a bunch of Lucas fuel injector in it. I let it idle in the driveway through a tank and a half of gas. Then I tried to take it up and down my street (cul de sac so no traffic) and barely got it back to my driveway. My driveway is on an incline and the car was running so bad that I could only coax it halfway up. I gave up. The next morning I went out to continue to try to let it idle and the car started up and ran better than it ever had. This went on for 4 full days. The next day when I went out to use it the same problem showed up. My neighbor suggested that I might try some drygas in case there was water in the fuel tank. I had him get me two bottles and have been trying to let it idle since. It is still doing the same thing. The only difference is that once it gets to the point where it's warmed up there is a lot of popping sounds. This entire time when it was doing this, once I coaxed the rpms up past 800/900 it would run smoothly without any noise all the way up to 2500/3000 rpms. My tel# is 910-233-2580 and I'd appreciate your help. I have arthritis

Answer
certainly sounds like fuel delivery issue, or alge in the tank/line.  Sitting for a year is not a good thing for these cars.
I would have the injectors and fuel delivery pressure checked, if that is OK it may be a vacuum leak as these are very sensitive to leaks
beyond that I would suggest taking it to a mechanic that knows how to work on these Kjet systems, they are complicated and computer driven, very sensitive to proper  adjustments and  cleanliness. .  I could tell you lots of things but best to start at fuel delivery (pressure and amount).  If that is OK then onto the next step
Good Luck