Oil Pressure - Kinda weird

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Hey guys!

First of all let me wish nice vacations to everyone! The summer is here and the hachi's need some km's on their tires!

Recently i've been dealing with a strange problem on my corolla.

Low Oil Pressure at idle!!!!

To let you know the problem itself i can explain what is happening and how, when i start the car at cold pressure goes to middle (2/4). When warm drops to (1/4), sometimes it goes to (0/4) but as soon as i press the accelerator and drive a bit it goes again to (2/4), the final stage is, when i really drive it RACE MODE, it goes to (3/4) sometimes even higher.....

So the problem here is, at idle it always drops to a low pressure value, but it responds immediately as soon as i press the accelerator!

My oil is Elf Competition 100% synthetic 10W40! The Oil is filled to FULL and the car is not leaking oil to nowhere!

What can it be?

Regards to all!