Normally I'm a big fan of K&N type filters. But in this case, not so. The angle of the filter looks like it's causing the filter to not be on there tight. And, the MAF angle isn't good.
Mass Air Flow sensors (MAF) are designed to have air flow across them linearly (straight). Putting a bend right in front of the MAF is a sure fire way to make air enter that MAF at an angle. When this happens, the sensor doesn't read quite right. This can skew things a lot more than you think. 10 - 20% would be my guess.
When this happens, eventually the O2 sensors will learn how to fix that. But at WOT, the O2 sensors are ignored, and the car will just run incorrectly by that percentage. Plus, when O2s have to work hard to learn, they tend to cause a drop in gas mileage. So no performance, and no mileage increase = why do it!
In this case, I would recommend either an aftermarket air intake kit (like a K&N cold air kit), or get a stock air filter lid, and buy a K&N filter flat panel type filter that's designed specifically for that truck. Also, being a truck, dirt is more of an issue, and the box lid design will help reduce that issue.
When you replace the lid and filter, buy some MAF sensor cleaner and spray clean the MAF sensor (the sensor right by the air filter). Particulary, clean the little diode looking wires inside the MAF tube. Also, when you reoil your K&N type filter, don't overoil it. This oil can get on the MAF sensor over time, and screw up the readings or even kill the sensor. (That's why I recommended cleaning it while you're in there).
