yeah you will notice a difference, i had the K&N CAI on my runner when i bought it and at first was happy about that, but then when i really looked at it and thought about it, i hated it, first of i didnt have the heat shield(like you dont), and so i was just sucking in hot air from the radiator and the exhaust manifold -not that the heat shield that K&N gives you really seals off the hot air... anyhow i dumped the CAI cone filter but kept the tube when i found a stock air box, used a drop in K&N filter for a while, but like others are saying, it just coated my tube in oil and the butterfly plate on the TB -though i never had any issues with the MAF sensor. so i just swapped that out for the factory filter, -i can get them free from my father inlaw so i just replace it like every 10-15k miles. and then i picked up a snorkel for dirt cheep($100), so yeah i noticed huge improvements in mileage, probably picked up close to another 30-45miles per tank if i drive easy, on average about 20-25miles using the K&N intake tube and factory air box with snorkel. im not sure if the snorkel is really helping things or not as far as getting more cold air, but i am sure its getting cleaner air, just because its not getting the air from in the fender and all the dust that the tire kicks up ect. -do i think the snorkel is worth the $450 for the kit just for the mileage? no, no i do not. but if you do wheel in areas that have "deep" water crossings or high dust environments like say you live on a dirt road, or spend a lot of time on dirt roads, then maybe its something you want to look into. but i dont think its something i would buy just to have for normal driving to help improve fuel economy or cleaner air on the hwy -it would take a long time for the savings in air filters, oil changes and fuel to cover the cost of the snorkel, and i venture to say that you would never put enough miles on the truck for that to ever pay off, even if you had done this on day one, and had 500k+ miles on your truck. -i know this isnt about the snorkel, but more about the CAI vs stock(ish) set ups, but sense i have the snorkel and it was mentioned by another member i figured id throw my two cents in here. yes i think it helps, and if you can find one cheap enough or get a killer deal on one, and dont mind drilling your fender for a permanent mod then sure you will "see" some slight gains(more if you live/travel in dirty environments), but honestly they will be hardly noticeable for id say 95% of people. i probably notice it more than a lot of people with it cause of having to spend a lot of time on back roads and old forest service roads and logging roads doing SAR missions. but still i dont even think for me it would be worth the cost of buying one new.
back to the original question, i think going to a enclosed style air intake system will yield gains for you over your current set up, and should pay for itself (especially if you can sell that old K&N filter). if i had the money id look into the volant system and try to seal it up cause i know that filter has better flow than the stock filter and its oil-less/dry if im not mistaken.
