MikeFish wrote:It's illegal though isn't it? I assume you are ok until the car is 3 years old and needs an MOT?
Nope, decats themselves are not illegal !
The car must still pass the emissions test, I've had cars pass decatted before. If it needs to be replaced in 3 years time the garage I use will happily swap it for the test for around £20 so it's certainly no drama.
This shouldn't void a warranty, they'd need to prove it was the cause of the problem.
It's totally stock sounding at idle in normal mode, you'd never know inside the car even when driving. If the Audi garage decide they want to test it in "S" at full chat then the issue won't be the decat, it'll be what justification have you for driving my car like that!
For the sake of a 20 minute swap and around £20 cost to swap I can decide depending on what works needing to be done under warranty whether its changed or not.