The inline fuel filter can be found on the right front body rail under the vehicle, below firewall
Here is Pontiac procedure
click belowFUEL FILTER
Best to have vehicle scanned for any Trouble Codes prior to Repairs
There can be a number of causes for the problem you described>Vacuum Leaks, Crank Sensor, Ignition, Fuel Injectors, Fuel Pressure, clogged CAT Converter, etc
The Heated Oxygen Sensor 1 (HO2S 1) is mounted in the exhaust manifold.
Heated Oxygen Sensor 2 (HO2S 2) is located in the exhaust stream past the three-way catalytic converter.