Yup...get the car to a competent mechanic.... don't park it for the summer.
In the scene of things it might be a simple fix....
If you smoke it...somke it UP THE TAILPIPE ....look for an exaust...
Might be the last of the simple diy things to check....
The flex joints can sometimes look intact...but be leaking... don't ask me how I know...once replace a cat on a Toyota Highlander only to find out a few months later it was likly the result of the flex joint starting to fail.....

 

You need to find someone in your area who specializes in BMW/mini and NOT the stealership. There's usually at least ONE in every major city.

Here in Omaha, there are a few major ones. Im sure you can find one in your city or near by.

Not saying your mechanic is incompetent, however it does takes some knowledge of these cars to diagnose them properly. Knowing the weak points are crucial.

As Zippy stated, the flex joint in the stock manifold is a known problem child. The joint is known for leaking and causing a p0420, p2096 nightmare. It may LOOK okay but a small leak can cause excess oxygen to enter the exhaust stream and tip off the oxygen sensor.

There are so many things that can cause the 2096 is crazy. And I hope you can find a mechanic who figures it out in your case.

 

I found a local Euro car specialist. After talking with them for about 30 min of possibilities, we decided to pressurize the exhaust to look for leaks and they found one on the exhaust gaskets. It was pretty small, but big enough to cause headaches. I now have a inefficient cat code to deal with, but that is much more manageable and I should be able to get inspected next week! the http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html should clear this one. Thanks for all of the help everyone!

 

Didnt want to start a new P2096 thread so hoping my issue is in line...I have a 2005 Cabrio S. Have serious acceleration stutter which leads to misfires and blinking Check Engine Light which then is ok after turning off car and back on but light still on.... Codes were P2096 and misfire codes. Replaced both Pre AND Post cat O2 sensors with NKG (OEM) sensors. O'Reily's scanner will clear them, but will show P2096 PENDING and it will light back up after 10-15mins of driving. Any ideas on the strong stutter/misfire when I accelerate Hard or in too low of gear and if it relates to this???

 

Sounds like you're not getting enough gas. check fuel pressur to start. can't remember spec off the top of my head but a quick search will yield results.

If fuel pressure is OK check injectors. Check Resistance. if they check out and fuel pressure checks out suspect pressure regulatorr or clogged injectors.

Just spit balling here but maybe your fuel filter is incredibly clogged. Either way you'll have to do some diagnosing to figure it out..

 

I would also clean (gently) the map and tmap sensors. They can get oil fouled and make the computer think the pressure is wrong, which makes it calculate fuel wrong..,

 

^^ x2.

Seen some dirty sensors do some crazy sh_t