Look to see if there is sticker or something on the ECM that specifically calls out whether it had a different tune installed. Or ask the original owner.
If there was a tune installed on ECM, there is no way of really knowing without comparing the cell values to a stock tune to see if they were changed.
You will need something like a Buelltooth adapter to connect the bike to a tablet or computer to transfer a tune over. This is a good place to start. https://www.rev-mo.com/
You can also use to it pull trouble codes and check various values such as AFV to see how it is running. If all is nominal, I would leave it alone...