Ran car without
MAF plugged in, revs don't hang with it off. Pinging slightly less but may just have been cooler air. Loose transmission on these cars make the rest of normal operation crappy if you don't get it perfect, clashing gears and rocking back and forth.
The pinging also seems to get a little less under full throttle so maybe it rules out things like bad injectors or crappy fuel pump/filter?