I have the same problem with my 260E, from 1988, 370 000 km
I changed the coil and many more hardware, and the problem is still there.
I have posted this concern under item called " 260E loss of power while running" and got many replies making good suggestions.
I would like to kow what to do to measure the fuel pressure while driving or check easily the pressure regulators have you any idea?
Performing this check could help.