The Barometric Pressure Sensor (BPS), located in the volume air flow sensor assembly, converts the barometric pressure into voltage, and then inputs that voltage (as signals) to the ECM. The ECM, based upon those signals, then corrects the amount of fuel injection, etc.
If there is a malfunction of the BPS, driveability of the vehicle will become worse particularly at higher altitudes. When it appears as though the BPS is malfunctioning, first check the air cleaner for a clog or restriction. A restriction of the air cleaner sometimes causes a reactions as though the BPS were malfunctioning.