mag48

I bought a car that had a turbo on it. . . I am changing it back to stock. The car is complete. It runs and drive but has problems. It idles and stalls. It will not rev above 6000.

The codes are

P0037 Rear HO2S heater control circuit low
P0171 System too lean
P0301 Front rotor misfire detected
P2004 ATC Valve open

I think the secondary fuel rail might not be seated correctly. I am not seeing any fuel.

I am also having problems with the fuel pump sealing ring not seating properly. Is there a trick to this?

Any easy way to check for vacuum leaks other than smoke?

Any help would be appreciated