Weird thing... On my '99 Protege, If you hold the car with the brakes and give a little gas, the brake pedal pushes back against your foot. I was going to sell the car and the prospective buyer took it to a mechanic who discovered this. Said he didn't know why. I tried it and it does push back. Could that be a vacuum leak? Bad booster? Would a check valve on the vacuum line help?

Thanks for any help!!!

Tocapet