I have headers on my XI, and this is how it went down during the phone convo with the shop manager:
manager: we will have to charge you about an hour extra labor
me: for what?
manager: I didn't know this was an XI, so we have to remove the front axle to slide in the headers. you can come into the shop and take a look before we start the work.
me: no, I trust you (i was 1hr away at school).
install was $450
I'm no mechanic, but trust the manager that he knows what he's doing.