Adding to this, check the vacuum lines, especially the little rubber bits that connect everything together. As these engines rely on vacuum changes to adjust the mixture, vacuum leaks can cause some strange issues. If you haven't changed the vacuum boots and you don't know when they were last done, replace them. Cheap parts, doesn't take long to do, and you'll notice an improvement, whether or not it's the sole cause of your running issues.

It is also worth mentioning that you can adjust the overall fuel mixture by adjusting the screw in the center of the air cleaner. I forget the size, I think it's a 3mm allen. With the engine off, push it straight down and feel for it to engage the adjustment head. The part you insert the allen into is spring loaded, you'll feel it drop down and "grab" the head below. Make TINY adjustments. 1/16 of a turn at a time. CCW should be leaner, CW richer.

Being a grey-market car, you won't have an O2 sensor.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]