John Shankle - Shankle Engineering - made a turbo for the 2L and a water injection system to go with it back in the 70's. The water helps prevent pinging at high CR, so you could use 4 - 7 lbs of boost with stock 10:1 pistons. Usually the alcohol is used as an antifreeze, not as a fuel boost.
John is out of business, but some of his systems are around.....
Having said that, water or water/methanol injection isn't so much a power adder but can let the engine make more power because it's a massively effective detonation suppressant. Turbo'd or supercharged engines are more often than not knock limited at some point in their rev and load range and require less than ideal ignition advance to control detonation.
If the engine isn't knock limited in it's power output (some strangled NA engine), then it probably won't add much if any advantage.