Testing fuel pump
I know one way to check if your fuel pump is working properly or not. I know u switched it out already but u might be able to use it as future reference. One way is with key on, engine running check the psi, then restrict the return line, and the pressure should just about double, but only do this for a couple seconds or you can damage the rubber diaphragm in your regulator. One way to check if the diaphgram is ruptured is to check your dip stick for a gassy smell caused by gas leaking into the crankcase. Another way to see if gas is in your oil is to check its flammability compared to clean oil. Now for failing the emission test, it might of just been from your custom exhaust, a CAT can make quite a difference, but who wants one of those?