In Southeast Africa, when driving, if you let go of the accelerator and step on the clutch, the idle speed will rise instead of falling, and it will remain at around 1300- 1500 rpm.

I think it's because you adjusted the throttle. When you have a certain speed, you put in neutral or slide on the clutch. It turns out that when the driving computer stops, the engine speed should be controlled to be higher than the idle speed, and the static idle speed will not be restored until the vehicle stops. There is a calculation ratio. Because you have adjusted the idle speed, there may be some errors in this calculation, resulting in a high idle speed when taxiing.