I've got a pretty big road trip coming up for the eclipse so I decided to take a crack at this again since, over the course of 3,500 miles in 8 days, I'll have both hot and cold weather to contend with and I'm sick of my windshield getting all of the love.

I was expecting an arduous night of searching for vacuum leaks at each and every junction but came across this thread, where CF member redeyes identified the actual vacuum line that supplies the blend door actuator. I located that hard line and it looked fine but when I went to wiggle it only one side moved. It had cracked completely in half but was perfectly aligned. I slipped a 2 inch piece of rubber vac line over the cracked hard line and everything works perfectly, now. We'll see if it has any effect on my fuel economy. Thanks for all of the advice and guidance.

The hard line actually ran under that corrugated wire loom with the crack occurring directly beneath it so there was no way to actually see it. Such a weird coincidence. This vacuum line exits a grommet in the firewall on the passenger side directly above the charcoal canister (on a RENIX).