2004 Infiniti I35 • 47,000 miles

Upon accelleration, nearing 1800 to 2200 RPM car begins to ping, w/further accelleration pinging stops or drop below this rpm pinging stops.
Also when running above this rpm and when release the throttle pinging starts
again at the same rpm. I use 93 octane, have tried octane booster, changed gas stations, trying blowing out carbon, changed spark plugs to Nissan factory plugs, adjusted timing with no change in sound. Do you have any suggestions? I was told to change my engine, but can't imagine changing my engine with so little mileage.
February 23, 2012.

Have the knock sensor checked.