brake related idle issue for 1993 s13

[remzon]

1993 240sx SE, 260,000 kms. stock everything except injen air filter and ignition system.

Hello all. wondering if anyone can help me out here... my 93 s13 sat around for most of the past winter spring and summer and i just started driving it again a couple weeks ago. did a bunch of general maintenance to bring it up to par like oil change, new fuel filter, new battery and new alternator(though it turned out all i needed was the main fuse) the issue is that when i depress brake pedal when i'm idling, RPMs drop 200, then will adjust back to proper idle at +/- 750. when i come to a stop at a light or wherever, RPMs will drop down to 400 or so, then go back to normal when i let go of the brake. i checked brake booster line and i have good vacuum and i also checked the one way valve, seemed ok. ANY IDEAS??? also might not be relevant, but i can hear rushing air in the vents when the clutch is not in, and the sound of the rushing air stops as soon as i put clutch in. i thought that was weird.....anyways any theories are much appreciated. THANKS!!

[574-240sx]

Sounds like a vacuum leak, get a vacuum/boost leak tester.