87 D21 odd noise?

[ray1377]

It started a month ago. It sounded like valve ping, or knock. I changed the fuel to 101 octane, no help.
Checked the cam and valves, all was well, no broken springs, valve lash in spec. It seems to only do it when the engine is under a load. Checked the cam chain and guides. Chain is tight, gears in great shape, no problem with tension guides.
Plugs, wires, cap and rotor are all good. Fuel filter is new, air filter is clean. Cranks and runs with no apparent noise until the engine is put under a load, such as climbing a hill.
All fluids are at the correct level, everything seems in spec. But here is an odd thing I noticed. When the pinging starts I can push the accelerator down and give the truck more gas and it will stop the pinging. Could it be low fuel pressure? Anyone heard of this before?
Thanks
Ray

[fontana dan]

Can you upload a video of the noise?

[ray1377]

I would if I were a bit more tech savy. Sorry
Ray