shouldn't be showing no boost up there. the boost should be only on the bottom of the blower. i'm not sure if you ever get a good vac reading with the blower, you are having to pull a vac. on the complete blower, and thats a lot of sq.ins. if your brakes are working ok i probably wouldn't worry about it. if it idles ok and have good brakes, you have enough vac. i ran stock cams a lot of the times and i believe the vac was always low, around 13-14" do you show any boost at the carb?