E39 help

[dpremley]

I will try to make this short, purchased a 528i E39 that someone started removing the head to replace the gasket, finished the job and put it all back together. I bought this as a project to be a daily driver. car starts fine and idles rough until it warms up then it runs perfect to a point, idle is dead on, no codes showing and then it will have a rev limit at around 2500 rpm and will not go past it.i turn the car off and restart and it solves the problem. then it will run for about 20 mins or so and then starts to overheat. I really need help in where to start on this, any help would be greatly appreciated. I am happy to provide any additional info or videos if it helps. I am not a stranger to wrenching but this has me completely stumped.

Thanks