would a leak in canister cause car to stall?

Question

My  car dies out when pressing brake pedal to change from park to reverse.

Answer 1

No, a leak in the canister if you mean the charcoal canister would not be the cause, You would have a higher than normal idle.  if the engine stalls from Park to Reverse, or even drive , the most likely cause is the IAC (idle air control valve) You can do a throttle body cleaning to help to resolve the problem