Brake squeal while coasting
 

this problem has stumped me for a while. I get intermittent brake squeal when coasting and slight throttle. the brakes don't squeal when braking, but only when I am in motion either coasting or partial throttle (does not squeal under full throttle). I have used a wire brush to clean my calipers as well as applied anti-squeal on top of the shims. I am basically stumped right now. I have Winmax W5 pads and stock rotors, though the front rotors have a slight lip on the outer edge of the rotors. could that edge be contacting the pads and causing the squeal? the squeal is only intermittent though, so I do not think that is the problem. I am thinking somehow the pads are sticking so does that lead to a caliper problem? I have made sure that the caliper sliders (the thin sheet metal pieces where the pads slot into) are clean of brake dust.