oil pressure is irrelevant, as it's the air pressure inside the valve cover that pushes the tiny oil droplets out the tubes. high revving will make the blow by worse simply by having more bangs per cylinder per second and churning up the oil in the valve cover so more drops can escape with the fumes.
all engines have some blowby, but the little tube is supposed to be sufficient for sucking all the nasty fumes out and putting it back into the intake manifold so it can be burned in the cylinders. in the end it's more annoyance that it's getting into the air filter than anything else. comes with old engines, but it's not a death knell or anything.