[ewill3rd]

I think you have more than one problem here.

The code should be related to the fuel tank pressure sensor. It is usually mounted on top of the sending unit on the tank.
For diagnosis and repair on your car I am pretty sure that calls for removal of the tank.
It could very well be a bad sensor.
It should not be related to the repairs you had done.

You could have driveability problems related to the starter install.
If someone took a shortcut and didn't replace the intake seals they may have created a vacuum leak.
This shouldn't really cause lack of power but it could cause a high or unstable idle and/or codes to set for a lean condition.

Whatever is going on with the engine should not be related to the pressure sensor.