I would think that if it weren't for the pinking, coils would usually give a complete hesitance or flat spot. The engine will rev as free and easy as you like, not a lot of power loss, just the pre-ignition noise.

I've been keeping it off noise as much as possible, pretty sure its blew the gasket but its not done enough damage to screw the plugs up so it can't be as bad as detonation but still seems a mystery.

Will have to try another 02 sensor I think, any other ideas welcome.