Originally Posted by sly335i
The key to any dealer attempting to Void your warranty for exhaust mod would be for them to prove the mod is the direct cause for the failure.
Wishful thinking. If dealer suspects a mod caused the failure they simply deny coverage. Plus they 'flag' your car, so every dealership will be aware of it. So the burden of proof is on YOU, not to mention you'd need to hire a lawyer to bring a lawsuit. The more reasonable approach is arbitration, like it was mentioned above, but if you messed with the ECU (any tune, including disabling O2 sensors), you're probably going to lose either way. And in you deleted the cats (a federal offense), your odds are even more bleak.
I personally can't understand why people risk damaging their cars and/or losing their warranties with anything other than catbacks and/or wheels when car is covered, but to each his own. No smart person (juror or judge) is going to deny that tampering with the ECU could have changed something that fried the engine, so that M&M is not going to do crap for you since most owners reverse anything done anyway before a dealer's visit. All BMW has to do is provide evidence of tampering and you're toast. And yes, at least the factory can easily do that. Good luck man.