First, the original air box offers virtually no significant restriction to air flow, so using something other than a clean original-type filter will have no improvement. Remember that you've got a n/a 2.3 liter engine -- it doesn't gulp air like a 7 liter V-8, even at high revs, so the OEM filter is not the limiting step in drawing air into the engine. What measurable restriction in air flow there is happens to start at the throttle body -- and you can't enlarge that.
Also, if you haven't scrupulously oiled the K&N (and possibly even if you did), the K&N doesn't stop dirt as well as the OEM filter. Do you want the engine to last, like Volvos do?

However, I do suggest that you modify the air box anyway. Here's the problem -- there's a thermostat inside it that controls a flapper the switches between hot air from the pre-heat duct from the exhaust manifold (directing hot air into the intake duct) and cold air from another, harder-to-see snorkel in front of the radiator. Naturally we'd like colder, denser air! Moreover, that thermostat is a disaster waiting to happen -- when it fails, it fails in the mode directing hot air to the engine and blocking the cold air. Eventually, when it fails, that continuous hot air will cook and destroy your AMM -- big bucks!

What I and many on this forum have done is remove the thermostat and block the flapper (I removed it altogether, with a dremel) so that the hot air duct is permanently blocked, leaving cold air to enter the engine all the time. Your engine won't miss the hot air, believe me.

Best regards, and happy holidays.