The M103 engine will not operate properly if the Plugs, distributor, rotor and leads are not tip top. This is your first port of call.

Then there is a tank filter, filter near the fuel pumps and filter on the intake of the fuel distributor. If these are clogged the car will not run correctly. I guess from your post that these were replaced after your tank cleanout.

Have you run a fuel cleaner through the system since the tank cleanout? There maybe some residual gunk that has been loosened from your tank that has got through to the fuel distributor and or injectors.

Always have at least quarter tank of fuel in the car to stop fuel tank gunk from getting in the system.

You may have fuel pump relay problems also.

You obviously have a 124 260E '88 model.