Fuel pressure reading for 5.3?

[C10CONFUSED82]

I am having issues with my C10 starting and staying running. I went to auto zone and rented one of there fuel pressure guages, really nice one. My reading at key on engine off is 51psi. With the engine on and idle its 48 psi. With the regulator disconnected from the vacuum line it jumps to 55-58psi. Is this okay? I have a external fuel pump feeding the fuel supply. Checked fuel filters and replaced one of them. The one after the fuel pump. There is two filters one before and after the fuel pump is this okay also? Thanks all to who reply back.
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