Hi, this happens to me again on a very hot day. The symptom is: all of sudden, the brake pedal becomes stiff. I mean I can only depress down the pedal just a little bit. Then when I want to accelerate, the engine works very hard and speed picks up very slowly. RPM will shoot to 3000. When I remove my foot from the gas pedal, the speed drops very fast. The car slows down much sooner than usual. So my feeling is the brake is dragging the car. The dealer cannot duplicate the problem during short test drive. So what can be wrong? The brake booster was replaced a few months ago. Is it possible it provides too much boost? Thanks.