Plug wires and cleaning grounds did very little to solve my misfire issue... plugs, contact cleaner, and fuel injector cleaner next I think...
That is surprising, I thought for sure the plug wires would have done it. I'd also run probably a full can of SeaFoam through 1 of the vacuum hoses just aft of the throttle body, and take your time going through the whole thing. That will at a minimum clean the absolute crap out of the IM, head and the combustion chambers. It could be some uneven carbon buildup that's causing the detonation.
Silly idea, but can you borrow an ECU from someone to see if there's something wonky with yours?