Pinging and bad performance

I have had a very bad pinging problem. with a 2.6L 4cyl with approx 97k miles. So far I have tried the following based upon "so called" expert
advice to no avaail: I drained the fuel and filled with premium. I used the fuel anti'freeze additiive incase any moisture was in the fuel tank. I rodded out the orife's of the EGR valve down into the engine block with a long fine stiff wire (kept this up for over 1 hour of rodding out). I tried all possible ign timing adjustments. I changed the routine parts inside the the distributor, i.e.: rotor, new cap, all new spark plug wires and new Bosch plugs were installed as well. I installed a new 02 sensor and nothing abnormal appears in the Diagnostic codes at all. I have not changed or checked yet the anti-detonation sensor that is located someplace on the engine block. If it is at fault, I will need to determine some way of testing or by-passing of this sensor. Are there any other tips, tricks or suggestions that you might could have me try? Thanks in advance. I'm running out of possibilities to attempt. ......... Ernie
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Sorry, I failed earlier to mention that this vehicle with the pinging problem is my 1990 Isuzu Trooper with the 2.6L eng.

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