Hi,
K&N sold an drop-in air filter, for the stock box that worked well, with noticeably improved throttle response.
When I exceeded the flow capacity of the stock air box (after going 50 trim CT26), I choose to purchase an Cold Air Intake tube from Spectre Performance, that I purchased through Auto Zone. It places the air filter in the space below the passenger side head light. The tube passes back through the stock hole for the cold air intake (to the stock air box) and onto the MAF in the engine compartment. I used an adapter to join the Spectre tube to the MAF, then sealed it all up with a silicone coupler and screw clamps.
The downside, the air filter now resides in a place that requires me to get on my back to crawl under the car to ge at it. Van