Brake Dragging, need suggestions

I have a 2001 Alero with 2.4L, auto, ABS and 60,000 miles. It was a recent purchase from a private party and I am still working out some issues. After driving a few miles at moderate speeds the brakes begin dragging significantly, so much that it will come to a stop on level while still in gear if I let off the accelerator. I inspected the front pads and found the passenger side was worn completely down on the caliper/ piston side. So I replaced the caliper and pads and bled out the line. I drove it a few miles and brakes seem to dragging just as bad as before.

Could the pressure not be releasing from the brake lines? I'm not too familiar with the mechanics of ABS, but shouldn't the brakes release fully once I take my foot off the pedal?

Try to spin all the wheels to see which one is dragging. A brake hose can go bad internally and cause dragging. You can check that by pumping the pedal then opening the suspected bleeder without foot pressure on the bleeder the fluid usually shoots out a bit if the hose is bad. Another cause is a pad that fits too tight in its anchor. Also pad anchor surfaces should be lubed with brake lube. But it is better to replace both calipers whenever one is bad.

Thanks for the suggestion. I replaced both calipers for the front brakes and inspected the brake lines and hoses and they appear OK.

I disconnected the fuse from the ABS system to see what kind of effect it would have and the it didn't effect the problem. I did notice however that the problem seems to appear at highway speeds or if I'm climbing a hill even at speeds of 25-30mph. It's not as much as the brake not releasing, but rather the brakes are self-applying.

Could it be a problem with the brake booster?