Have a 2001 Prelude 5 spd. Weird vaccum noise coming from around brake booster. Went to Honda dealer & they can't say for certain what it is. Dealer showed me that noise only happens after pressing down on accelerator. When pressing brake after giving gas, get weird vaccuum noise leak. Not like "hissing", but more like a annoying squeal. Have changed out hose form brake booster to intake manifold, but problem still exists. While car was running, disconnected same hose just from intake manifold, held finger to intake manifold port, pressed brakes, no noise. Reconnect hose, noise returns. Could it be brake booster check valve? If so, where & how do I get to it? Sorry for long intro. Just trying to be clear. Any helpful advise MUCH appreciated. The noise is driving me crazy!!!

 

Sorry, Ive done a search too. No luck. Please help if can.