Tyre pressures...for track time

[powerandtorque]

I aim for 26 to 28 hot. So i leave at like 19 front and 22 rears cold

Is there any reason to have the rears higher?

The OE specs on the Focus are supposed to be higher at the back, but I don't understand why when most of the weight is at the front.  

On a FWD car you'll generate more heat in the front tyres on track, and with heat comes increased pressure - so you'll find that you'll need to set the cold pressure lower.

OEM recommendations will take into account increased load from passengers and a full boot, hence the higher rear pressure recommendation I suspect.  Sometimes you'll see two sets of pressure recommendations from OEM's - one for unladen and one for fully laden, and it's typically the rear that is increased more for the extra load.