Robert, both sides are doing it. I think you may be right, its looking more like the calipers.
Sorry, but I'm not sure what a metering valve is, but I'm running a stock set up with seperate round proportioning valve and distribution block. If you take a look at the pictures I've provided, you can see them. http://gs106.photobucket.com/groups/m258/FO7JVC2QRD/
If I do have to replace the calipers, is there a better way to go than just replaceing the 4 piston calipers with the same stock ones? Would an aftermarket caliper be better given today's technology?