Tuning with jets, Power valves and an O2 guage

Boy that's a bummer, I wouldn't try a thicker head gasket, as you say your at about .056" on quench and don't want to get carried away.
190 psi is up there for pump gas engine ( I know, you know that )
Yeah, guys have made it work, with fuel injection, spot on quench, polished components, yada yada yada.
I don't buy into the current head gasket being your detonation problem right now ( could be A problem if it does over hang )

So for now, I like the thought of kicking that octane up to see where you are.
Then if you do a lot of driving you may be stuck pulling MORE timing out of it