01 7.3 Hard start and very rough idle... At first.

[S- Ranch]

Hi all,
I have a 2001 7.3, pure stock. No chips, no mods. Over the past few years, it has been progressively harder to start (turns over, but no catch) and running much rougher once it does (like it hits on 5 cylinders). After getting the rpms up and the temp up to operating range, it smoothes right out.
I have no codes, and had a buzz test done, 2 sounded different, but fired. I just replaced the GPR on a hunch, but no change. It is easier to start once the block heater is used... Had oil changes, new batteries, even tried sea foam thinking it was dirty injectors. Nothing makes a difference so far. GPs ohm out fine.
What else should I try?
Any help would be GREATLY appreiated!

[sldghamr]

ideas of things to check:
1. oil resevior for the HPOP
2. wiring for injectors under valve covers.

[S- Ranch]

Thanks Sldghamr, Im going to do some digging to find out how to test those. Ill let you know the results!