The bank 1 & 2 faults should have a fault code, indicating where the problem should be. A vacuum leak can cause a lean problem on both banks. Check the intake pipe hose for tears, allowing air to get in after the MAF. The big hose, also check the 2 CCV valves on each valve cover. The blue smooth is from the valve seals, on ly a thicker oil will slow that down, without replacing the valve seals.