Brake noise from piston?

I posted here a few weeks ago in regards to a metallic, scraping noise when I apply the brakes. The pads had meat left on them and I tried some tricks that Tifosi suggested to no avail. I was told by a couple of friends (non-Alfa experts) that the pistons vibrating in the cylinders might cause this. I installed new pads (all four wheels) figuring that they would cause the pistons to ride further back in the cylinders and maybe eliminate the supposed vibration. I used anti-noise coating on the backs. Noise still there. I noticed that the rubber dust boots are pretty well shot. Would this allow the pistons to vibrate? I'd like to hear from anyone who has had a similar experience. Thanks, RM