Using the datascan application and a decent emissions tester (good enough to give an idea of emissions) all saying that one bank of my engine is running lean. The drivers side O2 sensor is repoting very low or at time zero, also the CO2 reader that we have is reporting -0.8 while the passenger side is reporting about 3.4 3-6 What could be causing this? I heard the PCV valves can sometimes cause engine to run lean. They are only about 4 years old but its not been used at all in 4 years so may have clogged up. Any ideas?