Truck runs fine and a while back I had just code 171 and replaced the whole PVC assembly and the code went away but now I have codes 171,174, and 455. Im guessing they are all related. Can someone point me in the right direction.

 

Well tell ya what!
You didn't fix the first 171 code because it's back with it's partner 174.
These codes are related due to the same cause, an intake air leak affecting both banks.
The 455 is the fuel tank system diagnostics----- a gross leak detected.
The cap , fill pipe, stuck open solenoid or some hole, and not normally related to 171/174.
Good luck.