I have read that using a box kicks up an 'error' code TD1 that Audi can see.
Nope, you are confusing a remap with a tuning box. Those boxes aren't completely undetectable though, a black object under the bonnet is a dead giveaway plus, if anyone was capable of, the various sensors might be giving unusual readings. However I have never know one to be detected once removed.I have read that using a box kicks up an 'error' code TD1 that Audi can see.
Yes you'd be daft to give the dealership a get out jail free ticket...