The QR25DE engine doesn't use a VCT, instead it uses an IVT (intake valve timing) device to adjust the intake cam timing. The noise you're hearing could well be the timing chain assembly; worn out chain tensioner or chain guide. It's also possible with that many miles on the engine, the oil pressure may be very low possibly causing the chain tensioner to not work correctly. It may be a good idea to check it.
There's also a possibility that the water pump or the alternator is making the noise. An easy way to test those is to temporarily remove the serpentine belt and start the engine up to see if the noise goes away.
This is what doesn't make sense to me, when it's cold, it doesn't make much noise at all. But if I drive it awhile, it sounds like its going to come apart. I wonder if I use a heavier weight oil, if it would help? I did pull off the belt, still here it, I put a screwdriver handle against the front cover, I can here it inside. Next I'm going to pull the cover and check the guides and tensioner. I also have another 2.5 in the garage I can still parts from.
Before you pull the timing cover off, perform an oil pressure test; very easy to do. You can check the pressure by installing a temporary mechanical oil pressure gauge. You would remove the oil sensor which is located next to the oil filter and install the mechanical oil pressure gauge in it's place; you may need to get an 1/8 BSPT to 1/8 NPT adapter to hook up the gauge.
With the engine fully warmed up, the pressure should be as follows:
idle - at least 14 psi
2000 RPM - 43 psi or more