Im contemplating a new exhaust for the XF. My idea is to remove the rear cats and run a single pipe to the stock exhaust. I also want to open the muffler and remove all the insulation and the perforated kidney things inside then wrapping the muffler in sound heat/deading material . I am wondering of the possible negative effects on it. Is it goin to mess with the engine at all (backpressure). Im lookin for a deeper sound out of the exhaust. Thoughts and experience much appreciated! SORRY JUST REALIZED I POSTED THIS IN THE WRONG PLACE!!!!

 

Someone will move it.

I opened my NA muffler and removed all insulation, but left all the metal alone. Welded back up and made absolutely no difference. Might have even been quieter! I think if you totally gut it, it will make it louder, not deeper. Go for an aftermarket muffler in my opinion.

James

 

In the right place now

 

I haven't really looked myself, but if those cats have 02 sensors in or after them, their removal may cause fault codes.
I just swapped a Flowmaster 40 in place of the stock muffler until I can afford a full true dual system. The 40 did make it louder, but has a terrible drone from 2000-2800rpm. Above that, it sounds great. (eh, it was $60.)
I have listened to every exhaust video I could find out there, and there is one XF rallycrossing on Youtube; The guy has the stock cats, but true dual with Flowmaster Delta 10's and it is the best I have heard yet (it's all personal taste, though!) :
YouTube - ‪Custom Crossfire Exhaust‬‏

 

I went with a flowmaster and it sounded great but WAY to loud inside the car AND the drone was pretty bad too.

The rear cats can be removed w/out any o2 sensor problems causae the sensors are in the front cats. Id be sure to check with your inspection station to see if they will pass it w/out them. Im wanting to dothis mod but am getting mixed signals from different inspectors.

 

I worked at an emissions inspection station for a while. Every state is different, but here, on OBDII cars, We physically connect our system to the car. If the OBDII does not indicate an emissions fault, and there are no check engine lights on, we typically won't even look at the vehicles exhaust, or pop the hood.
If however either of the above happens, (and the OBD may throw for something mundane like a loose gas cap) we would do a full component inspection. The stations have books that tell them exactly how many cats and O2 sensors your vehicle should have. (almost all cars have an underhood label with this info also.) If it's not there, you fail.

My advice; if you do remove the cats, make flanged pipes to replace them that can be removed and the factory cats re-installed for inspections.