The OBD2 of today is extremely different and more restrictive in what you can do than the one in 1998. Its not even obd2 anymore. Its actually something like obd2.4 or something. Kinda like what the do with software naming with new versions. I deleted the cat on my 99 M3. It was very tricky but i got it to work. Then I tried it on my E36 2001 M3 and it was impossible. Just a waste of money I had to put the entire thing back into place Like it was stock Dont bother with it.

What's the point of removing the cats on an X5? It's a 5000 lb. utility vehicle, not a 2900 lb. VW VR6. You're going to get minimal HP gains while releasing more pollutants into the air. You're better off spending your money on a cat-back exhaust system and going for a sound improvement instead of an HP improvement.

But if you must, use an O2 simulator plug like this one:
http://cgi.ebay.com/ebaymotors/O2-Si...QQcmdZViewItem

Hopefully you won't scramble the ECU.

actually my vr6 weighed in at 2400 lbs with me in it. and i was 240 at the time... light weight reduction, but yea i jus twanna find out if anyone has done this and want to kno the pros/cons of it

Certainly it's doable. But if the E39 M5 and 540i owners aren't running bypass tubes in place of cats, why would you do it on an X5 with its additional weight and parasitic driveline losses due to AWD? Anything you do to an X5 engine is negligible in terms of real performance until you make the big leap to a supercharger.

I just removed the resonator on my 4.6 and added straight pipes and it sounds mean and clean. I don't have any of those buzzing or clanking noises that others experienced before they went to the X pipe. It gives it a little more rumble and nothing more, I had a B&B Triflow on my M3 and I think the straight pipes sound much better.

:iagree: