03 6.0 with fluctuating oil pressure

[PLUMMER]

Been having weird intermitent oil pressure problems. Made a 150 miles ride yesterday and just at 144 miles it starts to fade from 48-52lbs to 35lbs. Then you could hear the valve line ticking. Pulled over imediately waited 20-30 seconds started right up and no clicking or anything made it the rest the way and fine. New oil with 400 miles. Seemed to happen right after I had to get on it to merge into traffic. This has happened before a couple times and now it sems to happen anytime after the engine revs past 4000 rpms. I have done 2 consecutive engine flushes and oil changes just in the last 800 miles. Hoping to clean something up. I am hoping its not an oil pump problem but a dirty engine that can be cleaned. Swapped oil filters after each time it happened thinking it might help, not sure, but if it did it was only temporary or slight. Engine has had amsoil in it since 6700 miles, last oil change after the first symptom was ugly. now oil is clean.
Thanks in advance for any input

[DieselMonk]

What kind of oil did you use and what viscsosity? You have (had) sludge problems?

[Mark Rinker]

Are you towing during these problems? What is your water temp doing as the oil pressure is dropping? Something mechanical has changed, either the oil pump is failing, your fan clutch is not engaging soon enough, water pump not fully functioning, etc.

Hot oil is a symptom, not a cause.

[killerbee]

high pressure pump bypass valve would be my guess. On cold starts they usually bypass to the pan at around 90 psi for most models. It may be bypassing at low pressure.