Preliminary Checks

WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

Verify the customers concern by comparing the power output of a similarly equipped known good vehicle to the suspect vehicle.
Check the air filter for proper type and for dirt or restriction.
Check the transmission for proper shift pattern and downshift operation.
Check the PCM for the correct CNG calibration. Program the PCM if necessary.