so prob better to leave it on for the time being, especially since i overheated the other day It's unlikely to have much of an effect on engine internal temperature, at least not to that degree (pun not intended). I'd be looking closely at the state of your cooling system if I were you. It does however have a considerable effect on intake temps, which can effect economy/throttle response etc. Heat shields are best left in place for a variety of reasons. it's right.