For a N/A M112 engine you will need larger (possibly SRT6) injectors to give you adequate fuel delivery.

As to the Super Charger setup, be wary of too much boost as the internals of the N/A engine provide for a higher compression than the SRT6 and so will be more prone to failure at higher boost numbers.

As to the ECU tuning, the Bosch PCM that our vehicles contain are not suited for easy reprogramming. You may want to persue a piggy back system for a SLK 320 or CLK 320. (Almost identical drive lines).

Another option (more $$$) is to go with a Bosch racing PCM that is fully programmable from the get go. HDDP is doing this in his SRT6 Engine swap thread.

Hope that helps. Cheers!