I have a 2016 13" MacBook Pro with the 3.1GHz dual-core Intel Core i5 CPU and 16 gig ram. I have the latest release of Sierra installed. When I play YouTube videos in full screen either with safari or Firefox after about 3 min the computer starts to get hot to touch across middle of number keys, and the fans kick in wurring loudly. (This is without any other apps running) Soon as I quit out of full screen mode it settles down Can't open activity monitor in full Screen mode. Obviously if I do so with videos playing normally I'm only running with 10% CPU usage. I'm not sure if it's a hardware fault or software glitch that will sort it self out with an update. Given that it's behaving ok otherwise I don't think apple will find a fault to fix.