Does the CEL work?
Pinging and knock happens when the ignition of fuel in the cylinders happens while the piston is still moving up. This is usually because the mixture burns too fast after the spark plug fires (I'm ruling out incorrect timing because it's not adjustable).
The two common reasons for this are carbon buildup, and EGR malfunction.
Carbon buildup in the cylinders increases compression causing the fuel to burn faster. This is known as "octane creep" because higher octane gas is required to keep the knock from happening. Carbon can be removed from the cylinders by using water injection, a decarboning treatment, or a gas additive like Marvel Mystery Oil.
The EGR system reduces the peak temperature in the clyinders. If it is not working, higher octane gas is required to resist knocking. If the EGR is malfunctioning it should light up the CEL. The EGR passages in the UIM behind the throttle body get clogged eventually and need to be cleaned out. With your mileage you can safely assume this needs to be done. Other parts or the EGR system can go bad also.
