96 pinging very badly

i have a 96 olds bravada with 92000 miles
on it and it is pinging very badly. i have tryed 94octgas with no help it has newplugs/cap/wires/fuelfilter/egrvalve/all 4 O2seners and checkd for vac leaks what else could it be. i do not whant to damage the engen but it is my only car