You say that you put new mains in?

If so, did you check the tolerance or just replace with standard as that is what came out?

The tolerance needs to be there on the shells as if the gap is too wide, the pressure can drop excessively.

What grade of oil?

What is the pressure when @ 2000rpm?

2 bar when cold is only 29psi. I would expect to see a little under that when warm, when cold, a lot higher (almost on the relief valve in some cases).

Most pressure light switches come on around 12psi (or similar) I believe.