Duxthe1
Have you tried fitting EV6 injectors to your manifold? From what I can see, the injector holes and idle air setup is identical to the 8 valve M102 which was really easy to adapt to EV6 injectors. The injector nozzles are always under vacuum and are held down by the fuel rail as well so there is really no need to add another component to keep them down mechanically.
http://img.photobucket.com/albums/v242/tjts2/mercedes/DSC03114.jpg?t=1284984601
http://img.photobucket.com/albums/v242/tjts2/mercedes/DSC03116.jpg?t=1284984660
I'll get my hands on an M103 manifold in the next few days just to get an idea of any differences.
The throttle position sensor isn't really necessary for MS. I've had the M102 running without one for 15k miles now. All it does it fill in the gap between you pressing down the gas pedal and the MAP sensor reading a change in pressure. Even without any acceleration enrichment, MS has much quicker throttle response than any stock KE-jet setup i've ever seen.
If you're just doing a basic fuel setup, you don't need any toothed wheel. You can just use the negative terminal from the coil to get an RPM reading. I know people like to setup EDIS and other coil on spark type ignition systems, but the EZL system that is on the car is pretty good already. The spark timing maps on it are very good and adjustable, the only weak point is worn out distributor, wires and coil. Unless you're doing a turbo setup, I really don't see the advantage.
That said, your idea of fitting everything to the manifold (injectors, fuel rail, TPS, idle air etc) and then swapping the whole lot into the engine at once is a really great idea. It'll minimize your down time and you won't have any surprised down the road.
After doing MS1 to my M102 powered 190e, I'm looking forward to installing MS2 on the M103.