Sorry for the confusion but I am NOT worried about an axle-back modification, which is why I will be doing the OEM Exhaust Mod (non-perf). But I don't think that's going to provide enough sound in the cabin so I'm trying to figure out other options...
Technically even a dry air filter DOES void your warranty if it ends up causing a problem because BMW provides this part for free (this has been discussed in many threads and has been proven within the warranty language). I still haven't fully decided whether I am going to do a dry filter, as I understand that it is low risk, but I'm trying to see if there are any other alternatives.
Any other suggestions? Thanks for everyone's help!