Bit of a weird one this, when the engine is cold. If i go round a corner fast, so there would be alot of pressure on the rack. The pump will make a weird wurring noise.
The noise will increase as the engine speed increases, i can corner hard with it in neutral and it will still make this noise.
If i turn the engine off and straight back on the noise goes.
There is plenty of fluid in the system and it only does it from cold so i cant see it being a tensioner.