not to get off topic but, 99 and up brake booster's are hydro boost. you can trace the hose's from the booster to the power steering pump. they use the power steering pump to get hydraulic assist instead of the vacum assist on gas and earlier diesel's. that's why it's some time's hard to turn the while while trying to park or back up wwith the brake pedal pused down. the vacum pump we have on our truck's is used for ESOF 4X4 and the A/C and heater control's.
super kaz, there is supposed to be a schrader valve inside the pipe where that switch goes. the switch pushes down on the valve as you tighten it opening the valve. this allows replacement of the switch with out evacuating the system and recharging. give the service dept. a call to make sure tho.