Lean condition and MAF performance

A couple of months ago I had the water pump changed because it was leaking. Not too long after I had the check engine light come on and off. The car stalled at a stop sign and when I took it to the mechanic he said it was the MAF sensor so he replaced it. Has not stalled since. The check engine light still came on and off and the same mechanic said it was an O2 sensor. A family friend checked my car and replaced a coil, all four spark plugs along with the starter because it had trouble starting on two occasions. He also cleaned the top O2 sensor. There are times when the CEL is off and when I start up the engine it will make a weird sorta like a gurgle noise for a couple seconds which will trigger the CEL to turn on. Everyday when I start up the car the engine is loud and the rpm's will rise and fall between 1.5-2 rpm. A couple minutes later when the car beings to warm up the engine simmers down and the rpm huddles around 1. The CEL still comes on and is currently reading a P0171 and PO101 code. With these combined codes, what could be the problem?