Hi John
Just note that I gat probably same piston damage like you (top of the pistons untouched, but destroyed ring lands, ONLY at exhaust side of pistons). But Im using common WI (20% ethanol, 80% water), but reason was probably too high advance, what was about 25deg at top rpm/load for used boost (1.3bar).
Here is my original link
http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=1286
I really would like real reason of this damage, as now I have 8 broken pistons at my garage and thay are laughing to my stupidity everytime when I come around :roll: