rough idle 2008

I have a 2008 Sentra S with 73,000 miles. When I come to a stop with my foot on the brakes and in drive gear the engine idles rough at 600 rpms, but as soon as I release the brake pedal the the engine runs smooth and the rpms go to 750. If I have the A/C on the engine stumbles even worse. Could there be a vacuum leak in the power brakes system that are the cause and how can that be checked? Or any other ideas? Thanks.

if you run the engine for a few moments then shut it off you should be able to hear a hiss if you apply the brakes with the engine off. booster should hold vacuum until you apply brakes a couple times. can also tell if its working right by pumping brakes a few times with engine off, apply the brakes then start the engine, pedal should drop a bit as the vacuum comes back

if you run the engine for a few moments then shut it off you should be able to hear a hiss if you apply the brakes with the engine off. booster should hold vacuum until you apply brakes a couple times. can also tell if its working right by pumping brakes a few times with engine off, apply the brakes then start the engine, pedal should drop a bit as the vacuum comes back

I'll try that procedure this week. Thanks for the info.