2002 chevrolet Impala 3.6L no power when up to temperature

When the car is cold it runs great. When it reaches temperature and you come to a stop and then try to start up, it has no power. It will eventually pick up speed very slowly and then when it’s around 50mph and you step on the gas, it will take off and run normally. The fuel filter has been changed and it has been to serveral Chevrolet garages with no solution. When a computer was hooked up it registered no errors.

Someone will have to test some individual components like TPS and the other initials.

Has anyone checked the fuel pressure? When the engine is cold more fuel is being fed in. The fuel is cut back when the car is warm. Fuel demand is also higher through acceleration.

Of course, the actual speed of the car should be completely irrelevant (i.e. 50mph). Is it perhaps more about an rpm range or a degree of acceleration?

First thing I would test would be the coolant temp sensor.
The next thing would be the MAF sensor.