I'd be worried about that Tomo. Raising the idle speed is not fixing the problem; just disguising it by increasing the pump speed. If the oil pressure is low at idle, and the sender unit has the correct pressure for the NF (how do you know if it does?) then you will have low pressure at all engine speeds. The camshaft is only lubricated on the NF after the pressure relief valve opens, so it's possible that if you have low oil pressure the camshaft will never get lubricated. Possibly the problem is the oil pump, but the other possibility is wear on the bush that supports the crankshaft in the timing case. This bush is required to maintain oil pressure, but it's a really bad design, and when worn, allows the oil to leak past. Some people have fitted an o-ring or a proper oil seal in there, as the bush isn't required for support, only to seal, and allow oil to be delivered to the big-end bearing. I'm sorry, but I don't have the pressure at idle, but I think the pressure relief opens at 60 psi. Id I were you, I'd try an oil pressure gauge, so you can see exactly what is happening. If the pressure really is low, you risk some very expensive engine damage.