one of those $64,000 questions..
In principle, any modifications will have an effect on your warranty - however, the interpretation of how much effect it has will vary according to the dealer you are with, the nature of the work done, and of course exactly 'what' was done.
You are likely to find many variations in this.. from those who wish to keep their mods 'secret' from the dealer, to those who are totally open!
I had the same concerns, as mine is a company vehicle and I had to get approval before the remap was carried out..
AMD were superb to deal with, and impressed me with their approach, part being the concern that the remap NOT be so extreme that it for example then exceeds the specified torque limits on the gearbox - (their rolling road remap approach allows manual refinement of the remap) which would be a clear breach of fair play in terms of any potentail future warranty work.
Despite this approach, I negotiated that the remap be organised and carried out through their local audi dealership, giving me a formal AUDI invoice for the work - this cost no extra. This is STILL a grey area, and I think arguably such work still has an impact on the warranty - but done this way, and openly, I suspect any future negotiations on warranty work will be simplified, and much more likely to be restricted to just the items directly affected.
For me, this then was the only mod I could have done that would meet your criteria - as there is a superb gain in performance, with NO physical components being changed..
Others may disagree - bring it on chaps!
PS - the MOST important bit - whatever mods you do, TELL your insurance company - its simply not worth risking £20k+ of car by not telling them.. mine cost no extra, just an increased excess.
