Shine a laser pointer / pen on the clear fuel lines and you will see the air bubbles very easily as they travel through the other lines .
Tank strainer is usual culprit if air going into the lift pump , air gets drawn into line connections either at the tank end or where the rubber line joins the underbody steel line at the bulkhead .
Grey white smoke is lack of fuel / incomplete burn and in your case due to the bubbles in fuel.