Here is the car background: 1999 Pontiac Sunfire SE Coupe A/T ~110,000 mi.

In the last few days I have noticed a funny sound when I hit the brakes. It is a steady whooshing sound, like air escaping (or being sucked in) that is constant regardless of whether I am stopping or whether I am stopped. It has today gotten much louder and every time that I touch the brakes the idle jumps by about 500 rpm. Due to the symptoms, I'm thinking vacuum leak since my fluid level is normal. Anyone out there had a similar problem? Just trying to figure out if my replacing the vacuum lines will have a good chance of fixing it, or if I need to prepare to be raped by repair fees. Thanks.

Have you checked the vacuum line from the TB to the booster? It's quite long and snaked through the 2.2.

That's what I'm going to start with tomorrow evening or Saturday morning. So I'm not sure of its status yet. Though I did get a minute to check the fluid level which looked ok, at least today.

It could be the vacumn line, or it could be the bellows in the booster doughnut. If it's not the line, then i'd replace the booster as there's only 2 parts to that.
Don