I have had the OEM exhaust mod on my e92 for about 6 months now...definitely an amazing mod considering the money if you ask me. However, curiosity got the best of me and last night I installed a custom x-pipe with zero cats and four resonators. Paired with my modded OEM exhaust it is pretty loud with any prod of the throttle. Zero drone and fairly quiet at crushing speeds, but with moderate to full throttle it is really loud. It is a little too loud for me, so this week I will be reinstalling my un-modded OEM exhaust to try and quiet it down a bit. Hopefully this yields the results I am looking for.*
To conclude, it will probably be really loud. It sounds good and has good tone, but volume is excessive...at least for my taste. I hope this helps!