I am installing two TNBs (each requires about 1.8"Hg) in a aircraft using a 4" venturi. I have researched design information but Tony B does not mention this type of installation. My local chapter guru's are torn between series and parallel installations. Do I require a regulator, needle valve, series, parallel plumbing, what about hose diameter? Anything else I forgot? Thanks for your help. There are no other vacuum instruments in the plane.

Mark