Pull out the PCV and have a look. You may be feeding it 93 but of it needs 97.....
You don;t always here the detonation, especially at high rpm. Smoke or steam out the exhaust could be head gasket trouble. Also a indication of detonation from excessive compression ratio/lack of fuel octane. There is not free lunch. Water injection does a good job of eliminating detonation on high compression motors that really need more octane that whats at the pump.
I'd do a compression test and a leak down test to see how the ring seal is.