You are welcome.
There should be a plug located on the secondary fuel filter housing that you can install a psi gauge into. The engine does not have any inline filter screens.
If the fuel pump is the problem on yur engine, you will need to remove the HEUI pump/fuel pump assembly together. On HEP engines, you cannot just remove the trnafer pump from the HEUI pump. It iwll cause damage to the HEUI pump. THe entire assmebly must be removed and then there is a special bolt that is needed to replace the transfer pump.
Code 49 is a fault with the intake air heater. Not sure why that would come on after replacing the regulator. However, code 49 cannot keep your engine from starting.