I would do a search for 560 CIS fule injection. I remember seeing several comments is the past.
I would also look at the EHA and if you see any signs of leaking. Change it. The O2 sensor through the computer tweeks the EHA for the right mixture.
How many miles do you have on the car. I had problems with brittle rubber vacuum lines and nozzle holders that were broken. This was my problem.
H. O. Tyler
90 560 SEL 130K
85 300 SD 67K
83 240 D 260K