You actually have less compression on high cam due to more valve overlap. Since the intake valve closes later and the piston has risen up the bore slightly more then it does on low cam. I run a 12.5 static comp on my b20v. I use 98 ron and just retard the ignition timing till the ping is no longer exsistant. But i do run colder spark plugs then standard. Brk7e11's i use.