My Toyota Lexcen (VS Commodore) 3.8 litre V6 would also ping less under hard acceleration using E10.
This was before I installed an LPG system.
That brought it's own problems with backfiring, which I only learned later, was a well known problem with the Holden V6 on LPG. I was later advised to lower the gap of the spark plugs to 0.8mm and that eliminated the backfiring and made the engine way more peppy!
