Hi gents, trying to educate myself. Is the 510 verses 550 hp due to the x pipe exhaust and tune or are there other reasons?
Thanks

 

It's 100% due to the tune BUT as I have detailed elsewhere the tune doesn't "stick" (it reverts to a fail safe low power tune) if there is no X or H pipe in the exhaust system.
It least that is how it worked with putting an XKR-S tune on my 2010 XFR (Denso ECU), but it may be different with the 2012 - 2015 XFR which has a Bosch ECU.

 

thank you, it has nothing to do with my plan but was interested