Knocking Noise

After changing the sway bar bushes, replacing the tower arms, machining the brake dics, replacing the brake pads etc I can't shake off an annoying knocking noise.
It happens on applying the brakes and is most noticeable at about 30-40km/h.
Brakes specialists and suspension specialists can't find the problem. It sounds a metal to metal noise and I'm sure it's doing damage somewhere but I can't find out where.
It hasn't been lowered - still stock suspension - but it has 17's on it.
PLEASE HELP!!

CHECK for a lower ball joint recall on your galant