I have a 1998 Dodge Stratus with 157,000 miles on it when I step on the break the car idles very hard and wants to die. It has already died one time.It seems when I step on the brake the car wants to keep moving and its like it puts a strain on the engine.
You probably need a new brake booster. Though you should start by checking out the vacuum line and check valve for the booster.
There may be problem with the brake booster. From what you describe there could be a vacuum leak inside it and would need to be replaced if that is the case.