Re: New Problem/Comments/Questions
First of all, you don't need to fill up at Chevron exclusively, I mentioned Chevron by name because I thought it would be a recognizable brand. Shell, Mobil or any of the well known brands should be fine.
Carbon buildup is a natural occurance in gasoline engines because gasoline is basically made up of complex carbon molecules. One of the purposes of long drives is to enable the engine to 'blow out' any carbon deposits, this is where good detergent gasoline helps. One note, never rev the engine up (or floor it) until after it is at normal operating temperature.
Regarding the Techron additive, you should add it according to the directions on the bottle and it's generally a good idea to have the oil changed after you've finished the treated tank of gas.