I am ordering a K&N filter for the LR3. Picking up the truck today

I had put one in my old 97 Discovery and it made a big diference in gas milage.
Damn, this thread was getting better on page two....
Yrow, please do some research before you toss that filter in there, maybe talk with a tech or someone at Atlantic British. I have heard long debates over whether or not it allows too much dust in or something like that - not in cities, but if you go out in the desert, etc but still ask around.
Your engine running well with as few issues as possible is worth considerably more than some .05 mpg gain a silly filter would provide, even if it could do that. The other engine you had is not designed the same way nor is it's air intake science. Your best plan is very likely new oem filters.
The ONLY thing that's going to make big differences in mpg on an lr3 are it's resistance to air mass, i.e. driving slower and/or having a nice stiff 30 mph tail wind vs the same as a head wind.
My mom returns 16 mpg all the time in the 96 discovery...she barely drives the speed limit, hardly uses the brakes, accelerates sloooowly, and hasd nothing on the roof and no back seats.