Hi Steve,
I'm only running the LEEDS Electric Vacuum Pump without manifold vacuum. It has a pressure switch, so it keeps the vacuum adjusted as needed.
Here is the description and part #: Electric Vacuum Pump Kit - Black Bandit Series
VP001B
It works fine but I couldn't tell that the braking and brake pedal feel are any better than just running straight manifold vacuum.
The unit was $400 and I mounted it under the car in front area.