there is a another passage directly into the engine, semi-contrelled by the "regulator". I opened this device and noticed it does not completely close off the air coming from the discharge tube (actual design). I will try removing this additional air source into the engine to see if if has any effect on the idle. It will certainly during start up. Perhaps if I inserted the driver's side restrictor from the PCV system..? (I saved the old ones when I replaced the PCV hoses I had to cut to remove the plenum.)