Is it worth getting a custom tune
Currently I have an OTS Stratified tune. The engine is stock with bolt ons.
ATM my cars OAR is stable at -0.1 . This is with RON98 fuel. I have thought about putting some RON95 in when the tank is empty to see if it still reads -0.1 . If the OAR still reads -0.1 or very close to it, would I gain much from fine (custom) tuning it to RON98?