Just to tie a ribbon on this topic...it was noted that setting shadows to Ultra/4096 significantly helps the issue, but my GTX 1660 can't handle Ultra shadows. I can confirm this. Performance even starts to degrade with shadows on High. I think I am just going to turn shadows off. Between the speckles in cab, and the very unrealistic shadows at times (e.g., sharp, clear shadows when it's cloudy and raining), it just isn't worth it at this point.
Thank you everyone for the helpful input!
Matt