----
In terms of warranty some Audi dealerships have been quite good in terms of disregarding that they are there, however if you do have a subsequent engine management issue I wouldn't want to rely on them discounting its existence at that point. Best play it safe and always remove it before a service or warranty issue.
On the whole I've been generally happy with the DTUK box, the main gripe is that the impact on the smoothness of 245bhp engine has been very noticeable depending on the air temperature. During the peak of the summer heat I had to return my box to be reprogrammed as the car was stuttering on manual flappy paddles when working through the rev range. To Andrew's credit this was done without fuss and very quickly.
However, as the unit as no external ability to change the mapping program it means I have to remove the unit, take it apart, install it again, test, if not ok, repeat.... to change the program. I am now finding as the colder months have approached that is 9c and below I need to play around again to find the best map to put it on as its now stuttering again. I
accept the limitations of this as the car ECU invariably is reacting to the air temperature and the DTUK box is essentially a "manual" device that needs to be changed to suit, but if DTUK do offer a version that can be modified without having to remove it I would gladly upgrade to that for the convenience alone.
Overall power is all about where you want it. I've tried every single mapping and largely go between map 2 and 3 +1, (this will make sense when you read the install guides) I tried one map which put all the power down in 1st and 2nd which was fun for all of three minutes before you found yourself drinking a lot more fuel and attempting to rear end the car in front when you sneezed. Programs 2 and 3 give a nice broad spread of power 3rd, 4th and 5th being where its felt, that takes some tweaking depending on the weather but you really do notice it when you don't have it installed.
Hope this helps.