If your seeing 100 PSI on start-up, the problem isn't the bypass spring in the oil pump.

Normal cold oil pressure on a 2.6 is 100 - 120 PSI. Hot cruise you should see at least 70 PSI at 2500 RPM. As Eddy pointed out, if the block off sleeve is missing you will have a problem.

Noisy lifters can be metal in the oil or aerated oil.

40 PSI at cruise is too low, something is wrong.

On a fresh motor you will get a fair amount of fine metal as the rings seat, but no big chunks. I would cut the oil filter apart and inspect for bearing flakes.

You can inspect to see if the sleeve is in place by removing the balance shaft access cover. Kind of a pain to get at, but doable.