After years of taking car to dealer and each time asking what can be done to make vehicle run better on regular gas I finally discovered the problem. For about 2 years I was reseting the check engine light with a scanner that was complaining of oxygen sensor failures on both banks of the V8. I had a local shop replace the sensors for about $300 and the problem continued but a little less often. I finally searched the internet and found the the Mass Air Sensor can also make it appear that the O2 sensors are failing and the transmission shifts were sometimes erratic plus the pinging on regular gas. I bought a can of MAS cleaner ($5) made by CRC and as you can see by the pics it was pretty dirty, a few spays later and looked like new. Try cleaning before buying new at near $100 dollars. This sensor should have been inspected and cleaned if necessary when the air cleaner was replace but judging from the paint dabs on the screws this was never done.