2003 Ford Expedition Sensor says running lean and has a hes

My check engine light came on and I had it checked. The code said that my engine was running lean. At the same time the front AC stopped blowing and the car picked up a bad hesitation, not sure if these are related. The hesitation does not happen all of the time, just randomly. We could hear a vaccum leak coming from the elbow hose at the pcv valve. Changed that hose, but it didn't fix the problem. I also changed the mass air flow sensor, but it did not help either. After I changed these parts out I took it back and had the code cleared. It showed back up the next day and read the same thing. Running lean. Thanks for your help.