Evans Dash Air Nightmare

I have a 2001 HR Ambassador. The Evans Tempcon P/N on the molded plastic evaporator housing is the same as referenced, and also has cracks. I was able to find a couple of PDFs of a service and trading manual (the web link doesn’t have much other than a knowledge base with little knowledge). The Newmar training pdf has a schematic of a typical pusher install wth a vacuum pump and reservoir (troubleshooting guide points to this), but my install has a box with the 12= supply, the vacuum line to the reservoir and a red polyethylene line going to the back. Is there an option to get vacuum from the diesel? I didn’t think that worked with a turbocharged diesel. Anybody know?