That's not as much as I thought. Are the gtd remaps causing any reliability problems? Do the remaps get wiped if taken to a dealer for servicing or other work?
Never had any trouble with one

That depends if the dealer applies any software updates. If its been through the dealer network during the early years then chances are any updates will have been applied already
If it goes into a dealer just tell them not to apply a software update

if they ignore you then they will have to foot the bill to put the map back on