The rear AP Racing calipers have dust boots on the pistons. They go bad too. It's pretty easy to replace them. I had to remove my calipers (but could still leave it connected to the brake line) to be able to get my fingers in there. The boots themselves are quite simple to change, and are not expensive. I would use up as much of my $400 brake pads as I can instead of saving a $5 dust boot.
