I have a 1996 3RZ swapped into my '82 Pickup. I'm having some problems I need help diagnosing.

The engine is a 3RZ cylinder head and accessories from a 1996 Tacoma with a 2TR block from a 2007 Tacoma (the same internally as the 3RZ). All components have <130k miles on them. I had a local machine shop hone cylinders and mill the bottom of the head. I installed new valve guides and did a valve job (first time doing this). Main difference between the 3RZ block and 2TR block is that the knock sensor is in a different spot. I drilled out and tapped the 2TR block so that the 3RZ knock sensor would fit in the 2TR sensor location. Location of 2 sensors is similar, but not exactly the same. Other differences are slightly different oil pain bolt pattern and water bypass pipe mounting.

I have driven the truck around my yard but not on the road. But I have run it on jack stands up to 4000 RPM.

Symptoms/State:
--NO CODES
--Clanky/Marbly irregular racket (pinging?) heard between 1000 and 2500 RPM.
--If I remove all the load, transmission, belts, etc. racket (noise, pinging) sound pretty much goes away.
--Long-term fuel trim LTFT is at 18% at idle, raising RPM to 2500+ drops it back to 0%.
--Engine vacuum measured on gauge fluctuates 2-3 Hg around ~18 Hg.
--Between 1000 and 2500 lots of fluctuation ~7-10 Hg. Consistent with noises (first item).
--At around 3500 RPM the steadies around 18 Hg (more steady than at idle, almost still).
--Compression in each cylinder is 180 psi
--All injectors are making their distinct ticking sounds (monitored with stethoscope), so they ARE firing.
--Could not find a vacuum leak, and the vacuum does not appear ``low" just fluttery

--Running a 0W30 oil.
--I have an aftermarket fuel pump, Walbro Universal 190LPH External
--Injectors were confirmed to work out of engine with Amazon test kit and 12V source.
--I have added Race Gas so that my octane is 100+, and it still makes this racket. No change, before or after race gas.
--I cleaned my idle air control valve (IAC) and replaced the gasket, no big change.
--I have checked and rechecked my valve clearances and they are all in the middle (0.008" intake, 0.012" exhaust) or slightly tight 0.007", 0.011".
--I've also looked at the bottom end just by removing the oil pan and everything looks OK.
--I've run it with CAT + Exhaust, with just Exhaust. Exhaust is from a 22R, so perhaps a restriction?
--There is no suction back into the tail pipe, only outward pressure (good).

Any ideas?

Im going to try a new fuel pressure regulator (FPR) and throttle position sensor (TPS) next.

Help me get this baby on the road!