The pinging is back as of yesterday. Tonight I'm going to remove the intake manifold and see if it's clogged or my injectors are badly clogged. It ran fine with some fuel injector cleaner on the previous tank but now it's not.
I also noticed some oil in the coolant.
I suspect a lean mixture is causing the engine to heatup and warp the head causing a headgasket leak. Hmmm I'm thinking of a newer engine since this one has 250k miles.