oil pressure?

Well, your lifters are pumped up by oil pressure and will tap if pressure falls below what is required to keep them pumped. So, this would point to a real low-oil pressure situation. At least, it is plausible and you should not ignore the possibility of some sort of fault in the oiling system - bad oil pump, for example. Perhaps a mechanic can remove your electric oil sensor and temporarily replace it with a mechanical gauge and see what it reads. That would eliminate the in-dash gauge and sending unit.