34 Ford typical under floor brake system. I have ECI brake stuff. Front calipers are small GM Rear calipers are Corvette. M/C is Corvette, 7" single Booster. The problem I have is the car doesn't stop well in a panic situation. Under normal braking like coming to a stop at a stop sign works fine. I have the 2 psi residual valves, proportioning valve / distribution block all from ECI. I just checked the booster and all is fine except for the air tightness check.The test is, start the car and let it run for a few minutes then shut it off. Then step on the brake pedal several times and the brake travel should increase with each depression. Mine stays in the same spot each time I step on the pedal. They say it could be the check valve. I tested the check valve and it is fine. It holds vacuum forever with no leak down. They say it could still be the booster is bad. What are your thoughts?