After doing some research i think the best solution for a water/methanol injection will be a 2 nozzle solution. 1 nozzle positoned after supercharger/before intercooler to cool down air temp and 1 nozzle before throttle valve.

I agree with Brian Brave that MB engines are made to last long. If you want a race engine you have to rebuild them with race parts (which are rare, because there's in common no race intention from the drivers point of view).