This idea was presented in a video by Ted Brown recently.

The video contained the following information from Ted:

This is my design to get away from those pesky thermostat door openers. I went out today ran the car and started recording as the temperature reached 140 degrees F. These are connected to my EFI system vacuum circuit used for the idle advance. These are a vacuum pull, so if they fail, it will be in the open position.

I have no further details other than what we see here in Ted's video. When I find out more detail about this mod, I will update this post.

*Disclaimers