Higher octane fuel (91, 92) caused my engine to hesitate and have poor fuel economy

For some time, I have had a P0460 Check Engine light on my dash. It was first noted that it took a few seconds for my telemetry to register the engine temperature as well as the fuel level.
The P0460 code referred to the Fuel Level Sensor. Based on some research from online forums, it was due to the pump level sensor sticking, so I tried a number of different fuel injection cleaners and lastly this 91 octane fuel.

My engine was designed to operate with 87 octane fuel. Using a higher octane fuel had the following consequences :

• Hesitation in cold weather - this was not only worrying for the state of the engine but also the transmission, At higher RPM, there would be an occasional hesitation. If the automatic transmission is changing gears and there is a hesitation, it may have damaged the transmission. 
• Poor fuel economy - this was evident seeing the amount of fuel consumed for the few kilometers that I had driven - I only got about 10km/L where as I usually would get between 13 and 16km/L
• Contamination of my catalytic converter - Higher octane means reduced knocking for engines running at higher pressures and temperatures. The result in an engine designed to operate at 87octane means unburnt fuel being sent through the manifold and contaminating the catalytic converter. This also means the exhaust contained volatile organic compounds being sent into the atmosphere.

Bottom line : higher octane fuel did not resolve my check engine light code P0460 fuel level circuit. The higher octane fuel made my vehicle run poorly.