if i leave the air filter case split open where the filter itself can take in more air would that give a little more power? the way i am thinkin is if its covered how could it take in the amount of air it needs, so am i thinkin wrong or what? thanks

uh...well then its sucking in some of the hot air from under the hood which could rob some of your thinking. seems that if ya remove the inner fender snorkle thingy then close the air box up and let the engineering do its work, it would be more benificial

More air won't help you if it's hot air. It'll hurt you actually. Hotter intake air = hotter exhaust gas temps. If you can get more cooler outside air into the engine that'll help you the best.

Depending on what air filter you have(flat panel or round 97+ style) there's a few things you can do.

See if there's a plastic snorkel in the fender. If so, rip it out and throw it away.

the older flat panel air filter wasn't the best but it did work.

Most opt for the 97+ air boxes that the 6.5TD came with later on in it's life. There's two versions of that airbox. The "regular" version and the K47 version which takes a bigger filter. If you can find a K47 option air filter housing then go for it. With the 97 and up housing a good air filter(not a K&N) should be all you'll need.

Also make sure the little "connector" from the airbox to the fender is in place. That'll help you from sucking hot underhood air.

I have a K47 box and I leave the lid off in the winter, only.