Hi @mbeckmanUMHKN,
Welcome to the community! 
It is possible, I see that you already set your systems to Not Computed, but what you can also do to increase the performance or rather prior to synchronizing with the central model is the following...
Scroll down to your Families in your Project Browser >> Duct Systems >> Right-Click on a System >> Type Properties, then under Calculations, select you between the options which would work for you. (You'll need to do this for each system type.)

This is a "newish" implementation from Autodesk and below are two additional links to help you understand what each of the options will do:
LINK ONE (Scroll down the article a bit).
LINK TWO
I hope this helps! 
Rudi Roux
MSc | Digital Engineering Manager
LinkedIn
Revit Mechanical & Electrical Systems 2018 Certified Professional | Revit MEP & Architecture 2015 Certified Professional
AutoCAD 2015 Certified Professional | Autodesk Building Performance Analysis (BPA) Certificate
If this post resolved your issue, kindly Accept as the Solution below. Kudos are always welcome ⇘