What are your guys thoughts on this? Good? Bad? More power? More Sound?

First you want to check to see where your O2 sensor is in the order of things down the exhaust because if it is in the middle or behind the cat you need to have it as if the sensor is infront of the cat then you don't need it unless you want your air to fuel mixture to go to hell.

Also check your states laws because in certain areas cars have to pass an e-check or emissions check where you have to test the polutentes coming out of the tail pipe in order to get tags and if you have to go through safety inspection too then you need a cat or a very good look-a-like cat.

Usually after a cat delete the car does sound alot better but watch it around cops because they can still write you up for a noise violation which then gives them motive to check your exhaust. I hope your car runs good too because if it is off on air to fuel ratio then you will get a strong smell with the car stopped/idleing. You should also get a small gain in power too depending on how well your cat worked.

After checking all those things out if you still want to get rid of your cat be my guest and enjoy the better sounding BMW!:alright

what about a high flow cat? Could be the best of both worlds...

I'm curious to see the answer to this. In my work on turbo cars, less restrictive after the turbo is always better. But as I understood it, for N/A systems, the tuning of the engine is heavily dependent on the backpressure/reflected pressure waves in the exhaust, and modifying the exhaust w/o tuning has a good chance of negatively affecting performance.

I'm going to check it out. I am wondering about the O2 sensors as well. hmmm... only time will tell. I'll post an update tomorrow. Also if you guys must know the car isn't in the states, it's in Dubai. I live here now. There are only a few small rules! haha even real speed "limits" isn't something you have to worry about here. haha.

I dont have any experience with an exhaust on the 850's. However, i would recommend headers, no cats, and a reasonably quiet series magnaflow.. Some of the magnaflows are overkill. Also, if you are running under 400 or 500 HP i would think a 2.5" exhaust to be adequate. Certainly a cutting the cats is a must do, especially if there are no restrictions in the UAE.

I can't remember where I heard it but these V12's need back pressure somewhat so don't get to willing to break out the plasma cutter yet. Also have you seen the amount of room for headers or lack of I mean.

I've done this to an early E32 750iL. Replaced both catalytic converters with original mufflers (in Germany the cat was a factory option for the first few years) which had been modified to host the O2 sensors.
No change in power output whatsoever. Wasn't worth the expense nor the work.
Wolf