Hard brakes after a few hard runs

[ShadeTreeDSM]

I got an issue with my brakes getting hard like my booster is bad, but i dont see it being bad since it works fine 99% of the time, i know power brakes work off vacuum but my issue is after i run it hard a few times they get hard, and no its not when im in boost, its after i let off the gas, my boost/vacuum gauge shows 15" of vacuum when decelerating. that should be more than plenty to stop the car easily. i have the big brake upgrade from the n/t stealth with slotted/drilled rotors and a pads. Has anyone ever ran into this problem before ? im taking it to the track in 2 days and i wanna stop good, especially is my trap speed will probably be 115-130 mph

????

 

[talon2gb]

A long time ago my father had a caravan and the same thing would happen. Sometimes the pedal would be easy and sometimes it would be hard. It ended up being the seal where the brake pedal arm goes into the booster.

 

[Junior98gsx]

I got an issue with my brakes getting hard like my booster is bad, but i dont see it being bad since it works fine 99% of the time, i know power brakes work off vacuum but my issue is after i run it hard a few times they get hard, and no its not when im in boost, its after i let off the gas, my boost/vacuum gauge shows 15" of vacuum when decelerating. that should be more than plenty to stop the car easily. i have the big brake upgrade from the n/t stealth with slotted/drilled rotors and a pads. Has anyone ever ran into this problem before ? im taking it to the track in 2 days and i wanna stop good, especially is my trap speed will probably be 115-130 mph

????

Th pedal should be hard to push & the pedal should not bleed down to the floor & no sound of hissing air coming from the booster. If your getting theses results your booster is good. I dont understand your question fully does is take awhile to stop the car? Or stops hard?