We have been making this system since May of 1997 and have sold thousands of them so you can trust us when we say the Ready Brake will work perfectly fine with the power brake booster not being powered up in your towed vehicle. The brake pedal is attached to the Ready Brake with an aircraft cable and since the weight and momentum of the towed vehicle is pulling the pedal down it doesn't matter if the brake booster is powered on or not. If you are still not convinced, we will gladly sell you our Vacuum Pump Kit but we insist that our tow brake does not need it.