There is a three wire connection around the brake booster. One wire is hot, one is ground and the other comes from the pushbutton controller. These are all the info and horsepower the blower gets through the regulator. The wire that is from the pushbutton unit is the control. If the control signal is the same and the blower speed is different then I would agree its the regulator.
Bosch Master, ASE Master, L1
33 years MB technician