I have a 2017 Alterra 700. For the first 2 years it ran great in all conditions and temperatures. During cold weather now (under 30 degrees), it runs horrible. Misfiring and running very rough. If I warm it up for 10-15 minutes it runs reasonably. Checked the air filter, changed the plug, gasline antifreeze used, injector cleaner. No codes show up on the instrument screen. In warmer weather it runs great......any ideas??