This is yet another 2005 Ford 6.0L. Replaced HPOP, IPR, ICP, Fuel Regulator, EOT. After putting it all back together, I have a hissing in the secondary oil filter housing and I discovered that the Ipr valve loosened off a little. Questions: Will it effect the oil pressure if the Irp is loose, and will oil leak out? As well any ideas on the hissing noise? no fuel leak is visible from the outside.

 

What is the EOT? That normally stands for engine oil temperature, so I'm unsure of what you replaced there. Hissing in the oil housing will be bad, if you bleed off oil pressure, you're going to have problems. What oil filter and cap are you using? If the IPR is loose it will definitely effect oil pressure. I wouldn't expect a fuel leak if your oil cap and IPR are loose, I'd expect an oil leak.