Hey man! just came in see about check valve on fuel pump for my 280te 1985. I found a euro 280se with four speed and put it the whole drivetrain into my 280te wagon just want to say dont mess with the co screw there by the fuel distributor Until you have a cis fuel gauge set up to see your hot and cold fuel pressures vs your system pressure. When I passed emmission here the difference between pass and no pass was about turning that 3mm allen wrench co adjust about one Flat of the wrench.. if you are tempted just log your changes so you can get back to zero/start.. got lots of 280 w123 stuff.. good luck. till I saw you had changed it I would have said filter but back to check your pressures