Here is the K&N intake kit # 57i-2500 as listed for the Ford Explorer 4.0 SOHC European Models Only.

First the kit

Not much in the way of an intake kit. Really it is just a filter adapter with a mounting bracket.

To start then here is the original air filter box.

First step is to take the top off. As you would to change the filter.

Now you are left with the base.

You have to remove this and it is held at four points two in the bottom and two on the side by the wheel well.

After removal there is a metal base plate.

Lift the relay box off and undo the two screws holding it on.

Next mount the adapter with the bolts supplied.

This whole assembly is then bolted to the metal base plate with bolts and brackets supplied.

The plate is mounted back in and the relays clipped back on. Nearly done now just the filter to go.

The finished installation. A lot less restrictive that the original air box. Testing to follow.