I once bought an engine without original ECU unit at all. So i did have choice to find original ecu or bring own solution for that, and i did choose later option.So here is it, running fine on test bench: http://www.youtube.com/watch?v=qj0S2_57EU4&feature=player_embeddedThis engine (Audi 5cylinder TDI) has Bosch VP37 injection pump on it. I had to fully reverse engineer all controlling parameters for it. Configuration can be done over USB real time (ANSI/VT102 text-mode user interface), there is also Debugging and Monitor software written in processing which includes meters display, data logging and of cource - terminal emulator for to connect the boards UI.More information on my website: http://dmn.kuulalaakeri.org/dmn-edc/
Why use a Mega when the DUE is out now? The DUE has oodles of ram, as well as having a native CAN bus. It'd make an awesome ECM.