Getting code P0171 and P0174, which is lean on bank 1 and bank 2. I've already replaced the PCV elbow at the manifold about 4 months ago and inspected for vacuum leaks using break cleaner. Did not find any leaks. I also replaced the O2 sensor downstream on drivers side about 3 months ago so I'm assuming that sensor is still good. I also cleaned the MAF sensor using approved cleaner. I had the codes cleared but they came back about 2 days later. I've also noticed a knocking sound coming from the passenger side engine area. I've read in a few places that a lean condition could cause this issue. Any suggestions?