40-42cold for commuting and touring
35-38cold for twisty canyons
28-34cold trackdays
For twisty riding and especially trackdays, air/pavement temperature is a big factor. At trackdays, I typically start with a best guess cold psi. Then I adjust/check the psi almost every time I pit to 36 HOT front and rear.
For twisty/trackday riding with cold PSIs, the rear should always be 1-3 PSI less than the front. Most riders generally put more heat into the rear than the front, especially the Busa.