Is the check engine light on ????
A throttle position error or problem with the “drive by wire” throttle would almost always cause a check engine light ( aka CEL, MIL ) . The throttle by wire is responsible for idle speed. Sounds like off idle your still low on power maybe not all cylinders firing ??
Sounds like one cylinder might be in misfire or dropping out. 1200x does not have misfire detection so a problem with fuel or spark might not cause a check engine light.
Vacuum leak, pinched fuel line, bad fuel are also possible.
Touching each exhaust ( cautiously) after its running looking for a cold header pipe would indicate which cylinder is malfunctioning.
Any recent work done ? Modification, service work, accessory install etc......where a wire or connector could have gotten pinched or left lose or not completely plugged in. Especially a plug wire or injector connection.