when coming to a stop or slowing down my rpm (engine revs) goes up why?

Hello, Reading this post, I have only one concern, and it has to do with the brake vacuum booster. Pinch the vacuum line to the brake booster (google a pic, you can't miss it). If pressing the brakes is allowing a vacuum leak inside the brake booster, this will stop it. Here are some steps: Start the car, set the parking brake, leave it in PARK or NEUTRAL, and let it warm all the way up. Press the brakes - what does the engine speed raise to, and does it stay there or drop down? Please give me the full range like this: idles at 700rpm, raises to 1200 rpm, drops to 900 rpm (or whatever numbers you get). Clamp the line for the brake booster with whatever will pinch it flat, and press the brakes again. Let me know the numbers the same way if there is a change.