A friend of mine is looking to do a few motor mods to his X-type.  I'm
a big motorhead, but I know little to nothing about this car.

He's currently looking at cat-back systems (Remus, Borla), and a
intake/filter kit.  I figure the exhaust is at least good to free up a
little power.

I'm a little unsure about the intake kit, because it looks like the
stock airbox utilizes at least a cold-air style intake... if not a mild
ram-air setup.  The intake kit we saw was your typical K&N style open
element kit.

What other mods are available out there?  

Any computer/tuning companies?

Thanks,
-marc