Gary,

The nose tank needs to be non-vented. As fuel is drawn from the nose tank it creates a slight vacuum which draws in fuel from the main tanks.

I use tygon up to the pump and get nylon tees from an auto parts store, the type that are commonly used for automotive vacuum hoses. Also since tees add considerably to system restriction I buy oversized tees and force them into the tygon. For example if the saddle tanks are plumbed with 1/8 inch tubing I would use a 5/32" tee. Then the single line after the tee would be 5/32" tygon. Remember that the line after the tee has to flow twice as much fuel as each line before the tee.

Another way to reduce system restriction is to not use a tee. Instead install two vent tubes into the nose tank and run each saddle tank directly into the nose tank. You need to insure that each vent tube is identical and have equal lengths of hose from each saddle tank. Here's a picture of how I did that on my F-16.

Joe