1st Post. Limp mode on steep hill

Ok I had fault code P0110.
The car goes into limp mode (no warning lights) after driving over 1hour usually climbing a long steep hill.
I change sensor located just before air filter along with air filter, fitting safari snorkel and the issue disappeared until long drive (6hrs) hit steep hill at around 70mph problem returned. If I turn the heater on full heat it stops the problem. Do I change the radiator or intercooler. Why does turning the heater on stop the problem ?? 1st Post Cheers Ant.
Defender 110 2007 2.4 puma. It has been remapped by previous owner. But I think radiator and intercooler are standard.

Fault code P0110 relates to air intake temperature issue. I have attached relevant pages for fault codes from the 2.4 manual. As you do not have the last 2 digits for the fault code you will need to consider all the possibilities for P0110**. In my (limited) experience if changing a sensor does not fix the problem I have found the cause to be physical and something needs fixing (I had this with a MAF fault earlier this year). The intercooler sits between the air con radiator in front of it and the engine cooling rad behind it. If air flow is restricted the charge air will not be getting cooled and the sensors downstream of the intercooler will be sensing too high an air temperature and the management system will limit the engine performance. So my first inspection would be to examine the radiators (2) and intercooler for blockages in the fins.
I have no experience of remaps (personally I would not have one even if it was free as this could possibly mask faults which the standard diagnostic cannot read - but I stand to be corrected on this.
Edit: if turning the heater on full, this dumps a lot of heat and could be allowing the intercooler to cool the charge air a bit better. Hence the problem disappears

Just had a look at pic of your landy in the intro forum. The aftermarket radiator grille might not be too efficient at letting cooling air in. Also have you got a steering guard fitted? (might restrict air movement). And check the viscous fan is working. (trying to think of all things that might stop cooling air getting to all the rads).

Awesome, thank you. What your saying makes sense. Thank you also for the two PDF’s. I recall when I was under the car after the bonnet release cable parted trying to release the bonnet lock noticing that the fins in the radiator matrix were coming away, so I’ll inspect the general condition of both rad and intercooler. I have found a replacement front grill which is basically wire mesh... Thanks again for your time and info . It maybe some time but I’ll get back to you after the next long drive. It only ever happens on a hot day or after driving well over 2 hours.