Firstly opening the headertank cap when the engine is hot is the worst thing to do as this will cause the water to boil inside the engine and cause more damage than needed.

It sounds like you have an issue with the setup and tuen of the engine due to the way you say it was driving. I would advise getting it setup or at least looked at by someone who knows the MFi system inside out.

If you have issues with over heating the best thing to do is leave all fans running and try and get to around 50mph without using much power. Then after a mile or so pull over and turn the engine off for a min or two but leave the fans running. Then start it back up. This give the water in the rad a little time to cool down before it starts to move around the engine again. If you do this a couple of times it should help bring temps down quicker.

Then once the temps have dropped a bit get driving again to 50mph without too much power, if the temps rise again then you have an issue that needs to be sorted real quick.

Dont open tanks when hot as water when sealed with boil at 110degree if it has no cap its at 100 degree. That 10 degree diff can help save the block and headgasket etc.