I've had this problem for a while now. If I pump the brake pedal like 5-7 times or so pretty fast when I'm at a stop or in nuetral ( car is a 5 speed) the rpms shoot from the 900 rpm idle up to like 1600 rpm. Someone said it could be a damaged brake booster. i am going to replace the little in-line black thing on the vacuum line first...( I think it's called a modulator or something).

What do you guys think this is?

 

It's a rich idle condition. By pumping the brakes, you're adding air to the intake charge (via the vacuum booster). If idle goes up when you do that, then it's too rich when you aren't pumping the brakes.

 

Your brake booster "uses vacuum". That means every time it does something, it lets a little bit of air into the intake, via its tube.

It's normal. Some cars do it more than others, but all do it to some extent. In some cars, the RPMs change detectably just from one push sometimes.