The ignition should well be the power loss.
It does not take much of a chip in the relief to put a big hurt on the oil pressure on some engines.

Some worms need to be looked at. If that one bearing is uneven or is running tight now would be the time to know.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.