Re: 156 doesnt like corners
Air pressure settings should be done with the tyres cold.
I find 32PSI front 30PSI back is fine for general use, helps avoid wheel damage on the badly maintained roads around here. 32PSI front 35PSI back when fully laden and dropped to 28PSI all round in the summer when the tyres are more sticky and temperature increases more in use.
Most likely cause of dodgy handling.
I find that if I leave the backs over pressure without load, especially when I'm light on juice, the back end wriggles.
Remember that in wind, or on wet roads, the quick rack steering gets jittery as it needs such gentle course correction it can seem to be wandering.