Same applies to the MYP. All you get is significantly quicker acceleration to 60 mph. Carwow did some interesting testing in the UK and show even the P and LR AWD didn't pull the rear-wheel drive standard range model by much at a roll (70 mph). At 70 mph the LR was pulling the P if I recall correctly.This may be a bit of a misnomer / placebo effect; the acceleration boost upgrade does give a delightfully dramatic boost off the line, but at higher speeds the benefit drops off pretty quickly.
0-60mph acceleration has been documented to show an approx. 12% speed increase. 18-60mph increase is just over half of that at 7% increase. It drops off pretty dramatically after that. Check out this video w/metrics to learn more.
Tesla gives you exactly what they promised with boost and P, quicker acceleration to 60 and that is about it.