For what it's worth.......
I also had trouble with the front brakes.... They were dragging and showing brake dust on the wheels... I replaced calipers and pads thinking the pistons were sticking...Still had brake dust..The extra heat caused the one rotor to warp.. I wrote to another forum and the answer I got was to replace the front hoses... Though it sounded weird, I did it 'cause I had no other idea to try. But thinking about it, it made sense...If the inside of the hoses were comimg apart, acting like a check valve it could leave a little bit of pressure on the pistons, causing a little brake drag...After installing them I noticed the wheel spun more freely....It may sound like nonsense, but it worked...No more brake dust, no more warped rotors so far....