Whats this on my brakes?

[cwspellowe]

Phase 3's have electronic brake force distribution. As long as all the ABS sensors are connected and the rear brakes are plumbed in just as the old ones were you'll be fine.

Older 306's have a brake bias compensator valve that regulates rear braking force depending on the load on the axle. A bit primitive tbh and I did away with mine on the GTI6 in favour of a manual brake bias valve.

IIRC to pass an MOT there needs to be a way to adjust braking force front/rear but the tester I used had no idea what a manual bias valve was and passed the car based on its braking efficiency anyway.