Well, you can try a used throttle body unit... but usually there are no returns permitted if it is also bad.
Yep, suspect a bad TPS.....I tried all sorts of remedies including venting fuel cap, cleaning tank and cannister hoses and valves, fuel pump, fuel injector, spark plug, coil, plug wire and plug cap....nothing removed the stumble.
Started great, ran fast great - but big mid speed stumble.
Replaced throttle body unit under warranty - no more issues!
It DID seem to be very hard on the scooter cvt and engine to let it stumble so severely. ...so I parked it until fixed.
Please keep us posted on your experience.
Stig