welcome from arizona
while u r waiting take some wd 40 and spray the throttle linkages and move the rubber on the stepper and spray that. also open throttle and let it snap closed a few times.
Welcome John and partner from another Christchurch kiwi.
For what its worth, i had a 2014 Roadster i bought 2nd hand,at some stage it had been either dropped on its right side or similar which had bent the right side grip a little. This caused the throttle to stick when i decelerated...much like yours...
I took it apart and straightened it, put some graphite powder in there and she was all g.
Hope this helps and enjoy the forum.
...oh, be prepared for some good natured jibes from a few on here....you must have a good sense of humor to survive.