I've found the issue finally. Don't get me wrong, but the W900 Tuning Pack is nice, but it doesn't have all the lights or light choices I wanted. So today, I hit for the fences. I investigated every single thing I could find. I uninstalled ATS and re-installed. I disabled nVidia Experience App. I went into the files in documents. I even went as far as deleting the folder. So between desperation and anger, I re did everything. But, I would like to give a shout out to Roane Gaming for his 1.53 graphics setting on You Tube...big help. So.... I had his video going, and in sim changing different things in the graphics while driving in my Rezbilt 389. Pretty lengthy process. So, for your consideration, and for rejoicing to others who still love the trucks. Here you go. In game

Graphics:
Advanced Options:
Set everything else on Ultra or High depending on what card you have EXCEPT

Scaling: between 125 and 150%
Anti-alasing: SMAA+TAA
TAA Tuning: Adaptive Clarity
TAA Luma sharpening: 1.00

That's it. I dropped it from 400% scaling to 150% and the micro stuttering stopped. Game is still crystal clear. My Rezbilt 389 has lights all over it. In cab, micro stutter, out of cab not stuttering. By dropping the scaling down solved the issue.