Ignore DaveySaff!!!!

Your AFR's are spot on mate, combination of those AFR and that fuel should be very safe, I cant see you having det at the sort of timing you are talking about.

Can you not get a set of det cans on it and listen for det?

Failing that, its "off with its head" IMHO, better to spend an afternoon pulling it apart and checking than to just carry on regardless.