How old are the pads? Check for uneven wear; maybe there's metal making contact with the rotor. I swear, from day 1 I've had zero problems with noise. Lots of brake dust, but that was relatively easy to clean. I'm going to try out the Hawks HPS pads next.

My comment about the AEM's was that they weren't much better than the OEM units, but you may want to try them since your metalmasters don't seem to be working.

Shingo