SR20 PFC high knock.

Timing at point of knock is 8 Degrees BTDC at boost of 16psi, 4500rpm
Timing at idle is 15 degrees BTDC - verified with timing light

Fuel - A/F is at 12.0 at 4500RPM.

Shit spark plugs, checked and they look fine still. Perhaps i could try a different set at a colder temp range?