I have some audible ping at low RPM's between 1200-1800 RPM and low load .16 - .36 g/cyl, but it is not showing up as knock retard. I have retarded the timing in those areas pretty significantly to around 20 degrees and it is better, but am still getting some audible ping (again nothing on knock sensors).

I doesn't seem to make sense to retard timing much more. Just wondering if others have experienced this. (LS1 Texas Speed 5.3 heads (10.95 to 1 compression), 93 Octane).