Diesels suck way more air than a gas engine (of the same displacement.) That's why the airbox/filter is so huge. The one on the Pajero is more than big enough for our little 105hp 4-banger. As I said, I do have a K&N replacement filter in my airbox, but that's for the reuseability.

A bigger exhaust is supposed to help, according to "seat of the pants" reports on here. No hard dyno numbers yet. I can fully believe it helps the turbo spool up a little faster and may even keep the EGTs down.

1991 Mitsubishi Pajero XP TD LWB family hauler.