1994 Dodge Ram engine stalls on my work truck

My ram truck will start and idle rough and eventually the engine will drop RPM's and stall out. I have change the cap and rotor and also went through the spark plugs and wiring. That's OK. I have check the fuel pressure and it was 27psi when the key is turn on and 12psi at idle, so I change the fuel pump and still have the same problem. With the engine idling rough and engine stalling out. I also looked at vacuum lines and did not see anything out of place. Now when you press the brake pedal down it will stall the engine quickly. It's maybe a sensor but I not sure where to start.