you noticed a small drop because your engine is tuned for regular. it is running lean because of the oxygen content of c6h12o6. 2.5 - 5 percent leaner.
if you are typical stock and you are running 14:1 you changed to 14.7:1. if by some chance you are leaner than 14:1 you moved into a blow torch zone.
You lost me here. What are you talking about running 14:1 then going to 14.7:1? The stock tune is set to run 14.7:1 under most normal driving conditions, so I don't know where you are coming from with the 14:1. Please explain.