P0011 and P0021 Low Oil Pressure 2006 Xterra

[Surfschnauzie]

I recently replaced the broken main timing chain guide on my wife's 2006 Xterra (VQ40DE). Along with that I replaced the main tensioner, all of the guides, water pump, main timing chain, secondary timing chain, and secondary tensioner guides, temp sensor, thermostat, air filter, spark plugs.. When I put the car back together, at first, it seemed to run fine. However…
1. I get P0011 and P0021 codes
2. The oil pressure seems fine until the car is warm. Then it fluctuates, dipping exceptionally low. At one point the oil light came on, but not since I changed the oil filter and added more oil.
3. After I hit the gas there is a delay then a noise, but I cannot tell if it is an exhaust thing (the mechanic at one point said she needed new cats) or a rattle associated with low oil (unfortunately, I'm solo with this repair)
4. I get a code for idle relearn, but it think it is unrelated to my oil pressure/p0011 and p0021 problem.
5. When I had the timing case open, there was a semi dry oil caking around the timing chain guides and a coating of dried oil in the whole case. It didn't look like the timing cases online. However, with the exception of the broken timing chain guide, my wife does not remember a fluctuating/low oil pressure, which confuses me. After our mechanic repaired a radiator leak situation, she did have an occasional fluctuating temperature on the engine, but it would never overheat. The AC would periodically turn off (I think as an overheating safety mechanism).

Things I've done to troubleshoot:
1. I changed the oil filter. Fram to Purolater.
2. Pressure tested the coolant system (for head gasket) seemed to hold pressure. But I don't think that I ran it long enough for the thermostat to open.

Items that baffle me
1. My wife said she didn't remember an oil pressure light or low oil pressure prior to the main chain guide breaking.
2. I feel like low pressure may have caused the timing chain guide to break, with low pressure to the main tensioner.
3. I feel like there was something that might have caused the guide to break that I never found.
3. Why is the oil pressure issue only after warm up?

Please help:
1. Could it be that i'm not using an oem oil filter (if it is, why only the oil pressure issue after warm up?)
2. What is the variable timing cycle (could i be losing pressure after it activates? If so, perhaps I can narrow my search) How can I test?
3. Originally I thought it might be an oil gallery? How can I tell? I don't recall seeing a paper gasket slipping out from in the cover. - why only low oil pressure after warm?
4. On the cam covers I didn't put any new seals on the actual cover piece that goes into the cam (I didn't see any in the nissan parts diagram). I did replace the seals with the metal. I think there might be a seal on the protruding part of the cover. Could this be my low oil pressure when the variable timing activates?
5. Where is the passage way to feed the variable timing?
6. I never took off the rear timing case, is there a seal in there leaking and causing the low pressure? Does that seal feed the variable timing, hence P0011 and P0021?

Sorry for the wordy description, but hopefully someone can point me in the right direction. I would really hate to open the timing cover up again without any direction, or open it up when it turns out that I can fix it without opening it up.

[Surfschnauzie]

Ok, I changed out the cam seals. I put an OEM oil filter in the car.

Still the same low oil pressure and noise issue after warmup. When I first start the car there is pressure and no noise upon hitting the gas.

I tested the oil pressure.
When I first start the car at idle of 1,000 rpm it is 40psi and 40-55 psi @ 2,000 rpm.

after warmup

ONLY 3 PSI @ 1,200 RPM and 5 PSI @ 2,000 rpm and noise when I hit the gas and a loss of power.

is this the oil gallery? Is it the oil pump? Is it something else?? How do I tell? What can i test?
it is still running a little hot. I remember there was some oil buildup in the timing case

Please help!! Anyone please!! I need to solve this.

[ttiger]

Following.
I just did the same job on my 06 X and I have the same codes. Going to check oil pressure this weekend.

[macgiver]

mac,broken-off debris caught somewhere and it's "mobility" changes / "opens up" & moves to become"blockage" the hotter the oil gets (viscosity change).
Very tough one - if somehow to try "reverse blowing " some of the accessible passages back even to / or through open flange of filter "base" & better yet back through "some" of the pump galleys of block - I don't KNOW your engine though.
TIP: Use a stiff 12" pipe cleaner and "Dredge" the bottom of oil pan - through the drain hole - w/ a little bent hook to the end - any pieces of CRAP - like guide/tensioner plastic pieces -right ? I do this every other oil change -plastic and non-ferrous are not "picked-up" by my Magnetic drainplug!