Weird noise coming from brakes. PLZ help!

[Jehtte]

Okay, so I've noticed this issue for a while now, and I have no idea what could be causing it. Occasionally when I hit the brakes, this weird almost grinding kind of noise comes from, what I believe to be, the right rear brake. Now, it's not really a grinding noise, I just can't really think of another way to describe it. Anyways, It happens randomly, usually at slower speeds, (10-25 mph) and usually toward the end of the stop. I'll start to brake, and then once I've slowed down a bit, it suddenly gets angry or something and growls at me. It also kinda feeds back and pushes my foot back through the brake pedal. It hasn't ever caused a loss of stopping power, at least not noticeably, but I'm a little worried. The guy I bring my car to is a Z specialist, but he's never heard of this before, and whenever he drives it, he doesn't notice it. Could it be the ABS? Any help appreciated.

Also, I'm about to start Intake/bigger turbos/exhaust upgrades.(After I get this resolved) Should I go with Labree or B&B exhaust? I live not to far from Z1 and I think those are their two best choices.

[jaredta1a]

yes this is your abs unit, usually happens when it starves for brake fluid, if it hasnt damaged the unit already it will, and its not cheep to buy one. i hope you already checked the fluid in your brake master cylinder, if not check it and if its low find the place you loosing fluid and fix it then bleed your entire brake system systematically by the book.