Thanks for your comments. I'm following JA18's instructions in the Tech. Manual. Particularly, "Figure 3: Measurements with IP installed correctly" which I interpret, Pawel, as showing the #6 piston in the pump, the one closest to the firewall, as being 'down', ie. 5mm deeper than the #1, closest to the radiator. Based upon this, I'm still believing that the pump is installed correctly. Although it could have been installed 20° BTDC putting it out of alignment. i think, Shvegel, that I wasn't clear enough when I described the measurements I got. I was describing the cylinders #1 & #6 as being the cylinders in the pump. Not those in the motor. (See JA18's photos in the Tech.Manual.)
I have checked the vacuum advance and confirmed that it is working by using my timing light and watching the changes that occur when I press the accelerator. I did make an injector pressure tester and tested all the injectors off the car. They are functioning well. However, I haven't tested each line to see if fuel is arriving as it should. I'm thinking my next step should be to pull the pump and ensure that it is not intalled 20° BTDC. If it is indeed installed correctly, then the only thought I would have left is checking the arrival of fuel and functioning of injectors while on the car. I could do that.
A Last though. I seem to have a bit of exhaust manifold leak. Perhaps a bad gasket. Could this cause poor running?
Benz Dr. I know about that that 280 but never got around to paying a visit. Sorry to hear he sold. I live in a house built in the late 1850's and though it costs a lot to keep warm, i love old homes. Lots of history. I don't know who built my house. I wonder if it could have been the same person.