Try scrubbing the fuel injectors with a 1/3 of a can of seafoam in the tank and 1/3 sucked into the intake through the brake booster vacuum line.

Run 89 octane for a few tanks too and see if the ping goes away.

I'm thinking that scrubbing the injectors and the rest of the fuel system plus running a higher octane might clean any carbon deposits you might have. The deposits could be causing detonation.

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Sgtsandman's Work in Progress
2011 Ranger XLT, 4X4, 4 door Super Cab. 4.0L, 5 Speed M50D-R1HD, 3.73:1, 8.8" open differential, Jason Pace cap
2019 Ford Ranger STX FX4, Super Crew, 2.3L Ecoboost, 10 speed automatic, 3.73:1 with rear locker, Leer 100XR cap