The unknown valve on the left side is the heater control valve.Any tubing that does not leak and isn't kinked should be OK in place of the factory elbows,which are a little pricey.

The main reason I have found for vent selection problems is a defective vacuum distributor.It is located at the left end of the glove box on the heater case.It costs $200 dollars at the dealer but can easily be repaired.

Remove the under-dash panel on the passenger side,the two mounting screws,one wire plug and one vacuum hose manifold.Inspect the solder joints at the wiring connection with a magnifier and a strong light source.You will find one or two cracked solder joints at one end of the connector.Carefully re-flow the affected solder joints and your vent function will return.

Bill