I made some progress on the engine disassembly. I removed the heads and inspected the pistons and cams, which both looked to be in great condition. It appears there is minor damage to the intake valves on both sides, although I’ll have to remove the valves to be sure.

The pistons are surprisingly clean given the age ( 5 years ) and reasonable high power output/cylinder. I suspect that is due to the combination of high ethanol fuel (mostly E85 and E98), and the presence of water injection.

I have always been a fan of water injection. When I first got this car in late 07 I used a water/methanol mix, but in the last 6 years or so I have stuck to distilled water with a small amount (~15%) methanol to prevent freezing.