Have you checked out the radiator and the rest of the cooling system? There can be a blockage in the radiator that isn't always obvious. Run the engine until it's warmed up then shut it off. Put your hand near different spots on the radiator if any of them are cold you have a blockage. There are also thermometer guns that you can aim at different spots. The local parts store probably has them. They may even be willing to check it for you. Be very careful around hot radiators. I know a trained professional mechanic who received severe burns on his face because he leaned over an engine while it was running and the cap blew off spraying his face with near boiling coolant. This should go without saying but NEVER open a radiator cap on a hot engine.
Your 2000 grand AM could continue overheating even after replacing the intake gasket water pump and thermostat in case the thermostat was installed backwards. It could also be that the impeller was not changed when the new water pump was installed. With a worn impeller the pump could not move enough volume of water to keep the engine cool. You may need to get a mechanic to troubleshoot what could be causing the overheating.