Toyota Repair: Corolla engine light on again, vacuum hoses, air leaks

Question
I own a 2000 Corolla with 85,000 miles.  In the last year it has started to burn oil, about 0.25 quarts every 500 miles.  In the last 6 months the engine light has gone on 3 times after highway trips, always showing a P0171 code.  I have cleaned the MAF sensor twice; the gasket on the MAF sensor is beginning to get loose.  I have also used fuel injector cleaner after these episodes on a near empty tank of gas.  I reset the check engine light, everything seems fine, and then the next time the car is on a long highway trip it goes on again.  Could you please provide suggestions?  Thank you.

Answer
Using one quart in 1000 miles is considered normal oil consumption, you are below that. Check for any exhaust or intake air leaks, check for loose or disconnected vacuum hoses and the intake hose connected to the throttle body, if no leaks are found replace the MAF sensor.