I have 05 XJR and was wondering if the piping size is 2.25" or is it 2.5"?

Trying to get an X-pipe order to the correct size.

Thanks.

 

I kinda figure out the stock pipe is 2.25". Wondering if it is benficial to go up to 2.5" from the cat back with an x pipe straight to the stock rear muffler or just keeping it 2.25" with x pipe to the stock rear muffler? Keeping the two rear stock muffler for sound muffling but wanted a little more sound then stock hence why I wanted to delete the two middle resonator.

Thanks.