EXUP Servo motor
That error code relates to the EXUP (Exhaust Valve) being faulty, or in your case - not being there at all. It is not unusual for guys to remove the EXUP with the installation of an aftermarket exhaust system. The question is, is it a full exhaust system? I cannot see the need to remove the EXUP if it is only slip-ons.
Secondly, did the previous owner not Flash (ECU) or even PC (Power-commander) the bike after the exhaust install? If not, then the bike will run rough.
I am not sure if there is some other way of resetting the error without an ECU flash.
If the bike runs fine, then I would not be concerned - apart from that annoying engine light. In the current state you may have a real error, but will not be aware of it as the light is on all the time
Keep it real...