Sherman Hill FPS wonky for me

So when I drive the UP es44ac the fps dropped from 50-60 to now 40-50 but when I use the SD70m the FPS is better. I'd tried on other routes and the FPS seems fine though example morristown & coast line 60-70
Should I try uninstalling and reinstalling Sherman Hill? Furthermore, I contacted dovetail and they said " You appear to be running your GPU at a resolution it's not entirely suitable for please try reducing your settings if you wish to get the smoothest possible frame rate". How do I fix this should I fool around with the nvida control panel or fool around with the in game settings. Side note I'm using the 64-bit version.
