Recently, my 92 Spirit w/2.5 (147k miles) started pinging under load, I never heard this at all during the eight years I have had this car,. I have tried different fuel, verified the timing at 12 BTC and replaced vacuum lines. I do not have an EGR valve. I have a newer radiator and the engine temp is 1/3 up from cold. What other items should I check? I have no codes stored except the usual 55.