I did a quick search with +3.2 +sparkplugs and came acros this thread . I hope it works, its not very long, but describes the same issues you are having. But it also tells you which plugs to find.

Dan

92 Rodeo, 3.1 TB crank, custom bumpstop spacers, DOR shackles, Flipped ball joints, D44 Rear, 4.56s and new magnaflow cat and dynomax ultraflow muffler Since been replaced by a 2 door Explorer on 31's shackles, cranked torsion bars and full exhaust