Turn signal switch is broken. Have the same problem with the same car. Since the brake light and the turn signal are essentially the same light, if the switch for the signal is bad, it will effect you brake lights.
Brake Light 98 Monte Carlo Won't Work. All Bulbs Wiring Checked Switch Under Dash Replaced. Tail Lights And Indicator Work. What Is Wrong?
If you replaced the brake light switch on the pedal, I would test the circuit at that point. Is power getting to the brake light switch? When you close the switch is power going through the wire towards the rear of the car. Do not rule out that the replacement switch may be defective. Also, does the pedal actually activate the switch when pressed. It is possible that the switch is out of adjustment to the pedal.