I am pleased to report - I have solved my old problem - the air recirculate button not making the flaps close on the blower motor.
The original post is here :
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/932196-air-recirculate-not-working-2-minute-diy.html
This post might
Today I finally got around to this. I took Porsche part 944 572 709 00 - vacuum line, with rubber moulding on one end, and threaded it down to the open vacuum port from the firewall. I will try to find my pics of this. Since the vacuum line was rigid plastic, I could use moderate force and work the end into the open rubber hose port. I used a touch of dielectric grease to lube the vacuum line. I used a some long needle nose pliers I had that were curved on the ends - perhaps you know what those look like - and used them to help counter the force applied to the line so it worked into the port.
Started car, pressed recirc button, immediately noticed different air flow. Under the hood, verified the blower motor vacuum actuators were pulled all the way in.
As a bonus, I crafted some charcoal matrix add-on filters using bulk filter from the internet and hot glue, cut flanges from the matrix itself, and they passively sit on the blower input. Hoping not to get sand and odors blown in the cabin now.