I have a 89 EB (130,000 miles) with a 302 and an AOD. I have been fighting a pinging and surging problem for months. It idles fine, but under cruising conditions with a mild load is when it goes crazy (sometimes). This is what I have done so far: plugs, wires, cap, button, both fuel pumps, fuel filter, injectors professionally cleaned, egr valve replaced, egr sensor replaced, egr vacuum regulator replaced, timing is at 10 btdc with the spout out, fuel pressure checked, IAC cleaned, TPS checked, intake and throttle body removed and cleaned, checked for any vacuum leaks (none found). I have ran the codes about 6 or 8 different times. The only code that I am currently getting is 34 KOEO (DPFE problem). Just about everytime I run the codes I replace whatever it shows wrong, but I am tired of spending money without fixing the problem. I have ran 93 octane down to 87 octane it does not effect the pinging and surging. ANY help will be appreciated.