Starting and idling problems

Well this time I had 8 x 6.1 injectors that were working, put them in and had no real issues. At the 40second mark where I give it a bit of a rev it sounds like after I let off the gas that the engine revs drop below the normal idling point and struggles a little before fixing itself quickly. Perhaps fuel pump is an issue as the regulator seems to be doing it's job. I may have to get an expert in. See the video below. I pressume the rattle/groan from the PCV valve is normal, I had pulled it out recently and wasn't blocked and it still rattled.

[ame]https://youtu.be/KCzZIK23wyE[/ame]