Excessive brake dust

Current pads are semi-metallic and are throwing a horrendous amount of brake dust on the wheels - more on the left than the right - also pulls to the left when braking. Do I possibly have a seized brake caliper piston or would this more likely be a master cylinder problem? Also, in the morning when the vehicle is cool, if I get on the brakes too hard, I will only get one or two uses of the pedal before the brakes fade to almost nothing - its almost as if the system need a few minutes to warm up and pressure up the system. Once done, I let the vehicle sit with the engine running for several minutes and the brakes will work ok.:screwy: The rotors are warped beyond reason so I know that is a factor as well as possibly causing a pronounced shimmy in the front end.