ORIGINAL: akielb

By some law made a while back - no manufacturer can refuse any warranty issue due to an aftermarket part unless they can prove that it was caused directly by the modification.

Quote from Magnuson-Moss act
(c) No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the Commission if - (1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and (2) the Commission finds that such a waiver is in the public interest." (42 U.S.C. 2302(C))

ORIGINAL: akielb

What this means is they(audi or extended warranty) cannot deny/void/cancel your warranty just for the mere presence of any aftermarket parts on your vehicle and must prove that the product caused the failure. It is on audi, not you, to prove that the programing/lowering springs/oil that you use/K&N air filter...... caused the failure. All of this doesn't mean that they won't try to do just that - in the end it gives you the legal upper hand if it comes down to that. There are some dealerships that are chip friendly and some that are not. Burden of proof is on them and the law can be interputed many ways. This is how most aftermarket companies view the law -
If you are truly fearful of audi denying your warranty then take the precautions as stated above and get a second ECU.