Beyond the calipers, you may have an issue with your master cylinder. Do you have ABS? If so, are you getting a lit Anti-Lock light or if not, a lit Brake light? I ran into a similar problem with mine, which turned out to be a failed ABS master cylinder. My entire brake system was redone before that, new calipers and pads.
The brakes would be mush when applied, then the brakes would not want to release after a stop. Very dangerous. I would have to get the rpms up to about 2000 before the system would slack off.