It's odd that both are speed related... I suppose it's possible that the ECU is pulling timing and adding fuel when the temp starts going nuts.
I'd still start with looking into the cause of the temp gauge behavior. If the temp is bouncing around and it's not just a fault with the temp gauge or it's sender then the cooling system is crying for some attention.
I'd still start with looking into the cause of the temp gauge behavior. If the temp is bouncing around and it's not just a fault with the temp gauge or it's sender then the cooling system is crying for some attention.