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.
"The hardest thing is to forgive, but God does. Even if you murdered or robbed, yeah it's wrong, but God loves.
Take one step toward him, he takes two towards you. Even when all else fails, God support you.."
Cypress Hill x Rusko - Lez Go (Monista Remix)