Methanol has its main advantages in FI because of the ability to increase timing, not necessarily for just raising boost.
On a couple NA car's we have done testing on with relative scanning and diagnostic equipment, the car with straight methanol injection ran 6* of more timing on its own. That is a substantial amount of timing being added with a substantial amount of power. (Roughly 25 rwhp). This was on a 215 hp inline 6 motor.
On the S65 the gains will be beneficial, but don't rule out the corrosive properties of methanol along with the pressure added if water is added in the mix, as the water cannot compress.