Okay, so I've been doing a lot of research and reading a lot of threads about what other people have done to their XFR and the difference between the XFR and XFRS exhaust. The XFRS exhaust has the first muffler/silencer removed with an X pipe in place and less restrictive mufflers but it still has the resonator. I noticed, however, that many people that put an X pipe in place on their XFR removed both center boxes and have just an X pipe in place with piping going to the rear mufflers. I decided I will be changing out the rear mufflers for 5 inch Magnaflow round mufflers (or 'bullet style') and putting a Magnaflow X pipe in also. After all the research I've done I still have some questions I'd like to be answered.

My options are as follows:
-Change out the rear mufflers for the 5 inch round Magnaflow mufflers and put the X pipe in place of the first central muffler/silencer. This would be exactly how the XFRS exhaust is setup.
OR
-Change out the rear mufflers for the 5 inch round Magnaflow mufflers and put the X pipe in place of the first central muffler/silencer but also cut out the resonator.

So my questions are
1) Would one setup be better than the other? Is one more efficient or would both boxes cut out with the X pipe just be louder than with the X pipe and resonator? Does the resonator create backpressure? I've read threads where people cut out both center boxes and replaced with straight pipes and lost low end power, but once they put the X Pipe in place they gained that power back. This however was with the standard mufflers still in place.

2) From my research, cutting out both center boxes with the X pipe seems to be okay power wise, but since I am also installing straight through style mufflers (with a perforated core) will this cause a loss in low end/midrange torque due to loss of backpressure? Or will the X pipe solve this problem?

Basically the main thing I am concerned with is I don't want to be losing any power at the expense of sound, but I do really want a louder more aggressive sounding XFR.

 

I would go with the first option, will still be plenty loud enough but will sound more refined than the second option and there would be very little chance of power loss due to too little back pressure, while with the second option I suspect you might lose power and it's very likely to have annoying drone, especially cruising up a hill. That central resonator is there mainly to eliminate drone and it makes almost no difference to exhaust gas flow.

 

I think I will go with the first option, however, if the resonator has no difference to the exhaust gas flow as you said, how would option 2 result in a loss of power as opposed to option 1? Also, I noticed Jaguar setup up the XKRS exhaust with both center boxes cut out with an X Pipe in place, however, it is located further down stream. I've attached a photo. Shouldn't the X Pipe be placed as close to the engine as possible?

 

Exhaust gas flow and back pressure are two different things, although there is some connection. Greater back pressure usually correlates with reduced flow, but I don't think it's a linear relationship and I believe the resonators in the XFR exhaust cause only a small increase in back pressure, most of the back pressure come from the central muffler and especially the rear mufflers. That said, removing the resonators might just be the "tipping point" between enough back pressure and not enough.
Yes, in theory the X-pipe should be as far upstream as is practical, and Cambo has also queried why the XKRS X-pipe is so far downstream, but I don't think he or anyone else has found an answer to that question yet, it's a mystery!

Edit - I just noticed that the rear muffler set-up on that XKRS diagram is very much like the F-Type V8 set up, with a large central rear muffler (with valves), and not the twin mufflers as on the XFR and XFRS. Maybe that explains the location of the X-pipe?

 

The large central rear muffler in the XKRS could be why the X pipe is placed where it is yes. I will leave the resonator in place I guess to keep the extra backpressure (even though it is minimal as you say it could be the 'tipping point' between enough and not enough). So, you're saying the X pipe in place of the first central muffler and Magnaflow straight through rear mufflers should create enough backpressure to not lose power?

 

Maybe, maybe not, all I know is that many here who have deleted both the central muffler and resonator (with or without adding an X-pipe in their place) and swapped out the rear mufflers for free-flowing low restriction ones have experienced a loss of low and mid-range torque and power. Maybe even with the resonator in place the Magnaflow mufflers won't give enough back pressure and you will lose torque and power, but better to try it with the resonator in place to start with. Also, as I said earlier, without the resonator it is bound to drone, so better to leave it in place if just for this reason.