Valve train noises usually don't change with changes in engine load.
If it is quieter when the oil is cold suspect rod bearing problems--and there is, when warmed up, usually a speed where it will be a chatter or rattle.This may be up around 1500-2000 RPM unloaded.
At idle shorting out 1 plug after another may show a change in noise when the guilty cylinder is found.
An exhaust leak where the manifold joins the head will give an almost tapping sound that will go away when you let up on the gas.It will probably be worse cold than hot because the gap usually closes up as the hot manifold grows.
Again, valve noises usually don't change as the load changes.

Bob Taylor