There are a few reason this might happen. If the aftermarket intake has a different diameter on the piping the MAF sensor will need to be adjusted via the ECU (re-scaled). If this is the case take your car with new Intake to a professional Subaru Tuner.
In addition if the MAF sensor is dirty and the new intake is flowing more air you might get a poorly runing engine and/or ECU throwing CEL (Check Engine Light) codes. If this is the case clean your MAF with electric circuit board cleaner (make sure it won't leave a residue) and reset ECU.
Good Luck.
Unplug the electrical connection at the sensor. Remove the small bolt and retainer holding the sensor in place. Remove the sensor.
It does not have a mass airflow sensor.It does not have a mass airflow sensor.
It does not have a mass airflow sensor.It does not have a mass airflow sensor.
It does not use a mass airflow sensor.It does not use a mass airflow sensor.
It does not have a mass airflow sensor.
It does not have a mass airflow sensor.
It does not have a mass airflow sensor.It does not have a mass airflow sensor.
Mass Air Sensor (MAP) is defective.
It does not have a mass airflow sensor.It does not have a mass airflow sensor.
A Dodge Neon does not have a mass airflow sensor.
First find the crank sensor and then kick the crap out of it :D
A Chrysler LHS does not have a mass airflow sensor.