1999 Volvo S80 Brake light on; Tach, Temp, RPM shuts off

I just got this car today, used, and I drove it home. The car dealership replaced the master brake cylinder and said the brake light problem no longer exists. The cylinder did have a crack in it but they did replace it.

However I started it up in front of him and the car would shift from park into drive but the console still said I was in park.

I shut her off and turned her back on and it worked fine. I drove home and the brake light came on again. Then after getting off the highway and driving around 40 MPH just 20 minutes later the tachometer, temperature, and the RPM gauge would shut off and nothing but the brake light is on. When I would come to a stop after this happens it is as if the car is still getting gas when I am not touching the gas pedal. Its like a tug of war is going on with my engine. It even sputters a bit. I pulled over to the side and turned off the car and turned her back on. Brake light went off. The tach, rpm, and temp works. But then a few moments later the brake light comes back on.

I also noticed that the brake pedal is stiffer when the light turns on. When it is off it is not as stiff.

What could possibly be the problem?