I have a 409 hydraulic lifters, stock dual point distributor and 2 1406 Edlebrock carbs, I have a question on which side of the carb for vacuum. I have been using the passenger side of the rear carb for years and no problems but I just had them rebuilt and was told that maybe I should be using the driver side vacuum. After looking at the edlebrock website, it shows that the pass side is for emission controlled vehicles and the driver side is for non emission controlled vehicles. Has anyone else ran into this? How are you hooked up?