Not sure why, but I've recently noticed barely audible metallic pinking with heavy throttle application from 1,500rpm to 3000rpm. I might have to retard the timing a tad.

It could be a tank of low grade petrol causing the problem.

Anyway, it seems to suggest that running 21 degrees of advance is the absolute max of what can be done on standard unleaded.

Alanb

Oh std unleaded petrol, how nasty. Yeah a slight retarding of the ignition will sort out that problem easily, or cooler charge temp, then run MORE BOOST. If your a turbo owner that is!