I reality there isn't much of anything that will clean all of the carbon deposits off the pistons except pulling the heads and scraping the pistons.
The pinging is a result of the tune being off and a adjustment to the timing is the real cure for your problem, adjusting the tune is easier then pulling the heads.
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08 FLTR candy red sunglo,with 2015 103 HO, V&H Dresser Duals with Monster Rounds, Power Vision tuner, Willy Shiny Wheels and Forks and a bunch of other stuff.