Well you may have another problem but some extra stuff..........
1) when switching engine off to scrub e ensure that rpm is at max.
2) engine on, max rpm, min throttle will slow you up faster than engine off, max rpm. It has always seemed so.
3)check your keyboard map to ensure that your brakes are mapped as you think. (sorry if this is patronising........just worth a check)same for js map if on the stick
4) if you have toe brakes on your pedals then re calibrate.
5) if you have brakes set thru the js via a profiler (other than AH's) check that the key stroke time on/off and repeat function is set to duplicate a key that is "held down".