Is only doing it occasionally which I find strange, the low coolant level light is constantly lit on the dash even though I have full coolant I'm unsure if this is related though even when the car runs normal it's still there.
Any ideas? Appreciate it.

 

Could just be a sensor. I've seen a could have bad ecu that display this symptom too. Is it below or above 2k rpm or only on that this revs?

 

Is this on a Honda Civic, or a Ford F-150?

 

it's when I go above 2k that it starts doing it, drives completely fine under 2k & idles fine, revs out fine in idle

 

Again... Year, model, miles, anything?

 

When the car is in the limp home mode, the ECU limits the rpm. It's 2000 rpm max.