2003 chevy s-10 pick up manual transmission, changed front brake pads 3 times in 3 months. already changed master cylinder, brake calipers, brake rotors.

How about the brake hoses and lines? Get a friend to help you for a minute. With the vehicle up in the air and out of gear, spin the wheels one at a time and have your friend hit the brake and then release it. Try to spin the wheel again. Keep going until you find the one (or more) that is hanging and not releasing immediately. A deteriorated or clogged hose or line will apply hydraulic pressure to the caliper, but when you release the pedal, it can't bleed the pressure back off quickly enough, so the brakes drag.