Try re bedding them. It's helps a a lot with these pads. Mine were toast after two years on my old 330ci. I too had a lot of metallic noise with those pads and zimmerman rotors. I recall actually like those cheaper akembono pads over the HP.
"Player-haters turning bitch like they have vaginas ‘Cause we see them dollar signs and let the cash blind us.
Money'll brainwash you and leave your ass mindless..When snakes slither in the grass spineless.."