A screech is not normal with the brakes on or off. Since the sound is missing when you put on the brakes, the screech might not be brakes at all. Your SVT has disks in the front & rear so you might be able to see if it makes a difference if you use the hand brake, which puts on only the rear brakes. If the rear brakes are dragging you should be able to jack up the car, spin the rear wheels and hear something. I had a loud hum coming from mine which turned out to be an inner CV joint, but I had a heck of time isolating the where the noise was coming from. Try turning left, right, go slow and fast to see what makes the noise louder or quieter. Re-post your symptoms with some more clues and hopefully it will point to where your problem is. Hope this helps...
