I’d agree with Glenn, it seems the problem is elsewhere, I’d not advise turning the pressure up anyway as it puts undue stress on everything in the cooling system.

if it’s not a bad air lock or head gasket issues then I’ve heard of people use Evans waterless coolant, I can’t recall the results but it should help the situation.

Edit: and with the waterless coolant you reduce the pressure in the coolant system as iirc it behaves differently to water, it’s not cheap mind.