Signs of a chipped piston.
1. Car runs bad, you pull plugs and find one or more electrodes smashed.
2. Pieces of piston on top of your IC core. They can come up through the bypass hole of the SC
3. Visual confirmation
From research and chatting with others, apparently GM didn't gap the rings on the L26 and L32 as much as the predecessor engines. Therefore it's easier to chip a piston.
Max should be returning from a trip today. Likely we'll hear from him.