About the best mod, is remove the metal snorkle on the ait cleaner, and cut a hole on the other side so it doesn't run over the exhaust side of things, block off the original hole, then pipe it to behind the headlight as it was on the other side.
If you really want cut the metal besdide the headlight to get more in, but make sure insurance don't mind first :0)
Here's what I have just done. Mine was EFI on gas so that helped a bit with the different manifold. I recently took out all the EFI stuff and put in a mech/vac dizzy from an earlier XF. Total cost of materials for this = around $50 including cone filter