Q: Vibrations when I come to a stop

Boiling noise in engine after like an Hour of driving,when I step on the brakes the exhaust and engine vibrates when am at a stop but once I place gear in neutral or park all the vibrations go away.once I put it back in reverse or drive I feel all the vibrations.i just had 3 out of the 4 mounts replaced the Vibrations reduced but didn't go away totally as I had expected .i still noticed some movement in the engine when your Change to drive or reverse