Ok, the best way is to start by checking and testing the most common causes of these lean codes
First, check the pcv valve for being clogged, then check the pcv valve hose for splits in it as this is very, very common.
If ok, then test for air leaks of any kind. With the engine idling, use a can of carb cleaner and spray the air intake tube, all vacuum hoses, and finally, the base of the intake manifold one at a time. If the idle changes when one is sprayed, that is your culprit and you will need to replace it. Vacuum hoses and intake manifold gasket are the next most common causes after split pcv valve hose.
If ok, then clean the MAF sensor with electronics parts cleaner, followed by testing fuel pressure, O2 sensors and finally cylinder leak down test for sticking or burnt valves.
The majority of the time it is either a pcv valve hose or air leak
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