I have had engine pinging since I bought the truck -any idea what causes this?

What is your question?

Limited edit. automatic doublecab. I thought it was due to bad gas since it was bought in winter but it continued. I read in other blogs that other folks are having the same issue. They tried the higher gas but doesn't help. Happens on the slightest hills when rpm hits the sweet spot 1400. actually thought mice had made a home in air filter- asked the mechanic to check. There would be no way that I could trailer anything. So incredibly disappointed. Had 2002 new taco that was my pride and joy