I wouldn't trade my vacuum wipers for all the electric ones you could haul on a container ship. Mine have at least 500 speeds vs electric one or two speed or possibly three. They are also intermittent at ANY interval needed. I use a Mercedes diesel 12v vacuum pump ($20 at pic-a-part) mounted under the cab with a vacuum line run up through the factory firewall grommet. I send the motor to Ficken to rebuild and then drive it 30 years trouble free, uphill-downhill, loaded or not, or pulling a loaded trailer they will run at ANY speed I desire. I think the filtered contaminate free vacuum from the pump is better than the engine vacuum which could polute the pump innards when the engine spits back for any reason.

Evan