AMP pages slower than Desktop ???

I’ve done several Pingdom tests to see if it’s usually true that my amp pages are slower than my desktop pages. And yes, they are slower. Sometimes by more than 2 seconds.

Pingdom keeps saying the solution to the problem is “combine external javascript”

I put my test results on this page so that you can see them:
https://off-grid-insights.com/amp-pages-slower-than-desktop/

The page I need help with: [log in to see the link]