On Facebook forums a lot of the septics seem to think they're entitled to fit whatever they like, without any warranty issues. So has anyone here heard of claims being denied due to non standard parts being fitted?
Fitting a good quality exhaust system from the likes of Arrow, Akrapovic et al will not cause you any warranty issues. Fitting a botched de-cat, sub-standard system or one that?s clearly in breach of copyright and your dealer/BMW UK make take a different view?
Fairly sure there are BMW approved Akrapovic headers, that have cats fitted. I can see how that wouldn't be an issue. Systems without cats that aren't road legal, I'm not so sure.