hey guys, X5 Overheating, need some help please

[Secrets]

I've been having this overheating problem after the fan wear out one of the small coolant hose i didn't clamp properly. Some coolant fell out but didn't overheat. Replace that hose (which was the main one from the top of the radiator and the small one attached to it). After driving for a while (15 mins) saw the temp guage was going up. Stop immediately and noticed that big connector at the top of the rad came out. Apparently it wasn't on properly. Now here starts my problem: everytime i would go about 80 mph the temp guage would go up, once I slow down, the guage would go back to normal (halfway). The thermostat and waterpump is new because that was what i replaced when i didn't clamp that small hose. Since then I have replaced the fan clutch and the radiator but the problem still exist. I've tried to bleed it as much as i could according to the bleeding procedure i've read, but still overheating. Now this is a 4.6L and going 80 mph is like cruising with this. I would GREATLY appreciate any ideas or inputs anyone would have to help my problem. Thanks Guys. Note: All parts are geniune including coolant.