If you need to do the CAT ( if blocked) then do it, if not then leave it alone it makes no difference taking it out. (people who say otherwise just charge you for the job and then sell your CAT for a few thousand)
If ad blue is an issue do that as its not really needed in SA its just an emission thing for Europe.
DO NOT do an EGR delete it effects the gear changes.
There are gearbox failures due to it.
As for a remap. Do that at your own risk. ( there is corrupt software floating around that causes other issues,)
All the guys that do it just increase fuel and dont bother about anything else, it normally ends up with poor gear changes hot motors and more bills. Maybe not in the short term but def in the long.
And yes I speak from experience.
Best thing to do is change all oils , motor, TC box, auto box and diffs.
And then reset the Gearbox.
When you drain the auto box drain the Torque converter as well.
That alone will make your car feel like a new car.
Hope it helps.