The brakes generally work well, however when I have to make a hard sudden stop, a loud groaning sound comes from the general area where the brake equipment is. In addition, the front brakes lock up. Also, before I did a lot of work on the engine, replacing various worn out items, such as vacuum hoses, the engine would lose power, and stall if the braking was hard enough.
Replaced the booster about a year ago.

Any suggestions? Thanks!