The Mass Airflow (MAF) sensor is on the air intake duct right at the air filter housing. To check the MAF sensor, look for poor connections, inspect the harness, check for leaks, make sure the correct 
PCV Valve is installed, and ensure the oil filler cap is tight. To replace, disconnect the negative battery cable and disconnect the electrical connector. Remove the air cleaner assembly and mounting bolts, loosen the clamps, remove the intake air duct, and remove the MAF sensor. Installation is the reverse of removal.