2010 Prius strange "clicking" Noise when ICE is on

2010 Prius with 260K KM (160K mile) – The car has no problem except a bit oil consumption which is typical for the 2010. Started to hear some kind of quick clicking noise when accelerating lightly with the gasoline engine. Doesn't matter if the engine is cold or warm, going straight or making a turn, the noise can come & go at any time. Most noticeable at lower speed (due to lower tire/road noise?). No noise when the gas engine is off, i.e. the car runs on hybrid battery only.

I ruled out the possibility of the Prius infamous "morning death rattle" as the noise sounds much "lighter" and there is no coolant leakage.

It sounds like some thin sheet metal vibrating under the chassis. Checked for loose exhaust pipe or heat shield. But all parts are secure & not loose.

The car still runs perfectly fine as far as I can see. But I'd like to find out the cause and eliminate the noise. Does anyone have any idea?

Also just cleaned intake manifold, EGR pipe/valve/cooler, PCV valve not that long ago in 2022.

 

Low oil pressure... Mmm, never thought of that.
Should have a check oil light if that's the case, right?