Pinging on a new GT with only 3500 miles on it is not normal. My 04GT/Autostick has never pinged under any driving conditions. If available in your area, I would recommend trying Chevron Supreme (91 octane) gas which I have used exclusively in my car with great results. If your spark plugs gap was set incorrectly at the factory this might also be a possible cause of the problem. The recommended gap is .050. When my plugs were recently replaced at 15K miles the gap had expanded in all of them to .055. Inspite of this gap increase I never experienced a pinging problem. Good luck.
