brembo porsche rear brakes as '05 echo fronts

[ahdee]

so i bought a pair of these (drilled holes to fit, etc) and installed them, but after a few minutes of driving, it squeeks... LOUD! 99% of the time, it doesnt squeek upon the first few minutes of driving (when the brakes are... cold, i guess?). but after that, whenever i put pressure on the brakes and my speed drops below 50-40km/hr, it'll start a high pitched squeeking sound emitting from, ofcourse, the brakes. and it'll keep squeeking as long as i apply pressure on the brakes until i come to a complete stop. the sound will also stop if i apply a large amount of pressure on the brakes... ie.) brake much harder or slam on the brakes.

any ideas?