Thanks for the thoughtful response.
I confirm that I have no check engine light coming on and have seen no Code being generated other than a driver's side airbag light that I am working on separately. Question: How long would the Code last? i.e. as the fuel drops to 3/4s full and the gasoline smell goes away would the Code disappear then? i.e. should I test for the Code when the tank is full? Or would the Code last longer?

I did have a slight hiccup of power delivery when driving the car while the engine wasn't fully heated up when accelerating slowly around 1,500 - 2,000 rpm. Could this indicate a gas cap with a faulty seal? And Yes I have ensured the fuel cap is properly screwed on. But this slight hesitation seems to goes away by itself.