Mass Airflow Sensor (MAF) is a component of the electronic fuel injection system installed between the air filter and the engine. The MAF sensor is used to measure the amount of air entering the engine. This measurement is used by the engine computer to calculate proper amount of fuel injected into the cylinders in order to provide optimum combustion and low emissions.
A contaminated MAF sensor can cause a wide range of various vehicle driveability problems such as stalling, especially when the engine is cold, misfiring, poor acceleration, etc. HKS induction kits seem to carbon up the measurement wire more than others.