Overheating

There are a couple other things that this could be. The most likely is a partially open thermostat so if you replaced that then we need to rule out the worst thing, the head gasket.

So, let's run through this guide and see what turns up by checking the head gasket after the engine is warmed up. I would suggest using the chemical tester that is shown in this guide:

https://www.2carpros.com/articles/head-gasket-blown-test

Also, here is a guide that talks about the other major items:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

The next likely item is a failing water pump. The reason is, when you accelerate you are speeding up the pump and that will cause the coolant to move faster.

The last thing would be a restriction but if you flushed the cooling system and have good flow then I suspect we will find something with the other items.

Let's run through this and go from there.

Thanks