What started out as a simple day of dyno testing left us with a bunch of things that make you go, "hmmm."
We headed over to AEM's Hawthorne, California, dyno facility to put a Brute Force intake on our project TJ, Red. We had an aging Airaid system on it, the filter was dirty, and the metal screen that retained the cotton was actually broken in places, which allowed the cotton to escape and left spots in the filter with way less element than it should have (we don't even want to think about cotton balls in the combustion chamber).
We took some of our own advice and decided to put a dry-element filter on the Jeep, and while we were at it, run some dyno pulls to see what the actual increase would be. We dyno'd Red with the stock box, two kits, and some various permutations of it all. What we found surprised us and the dyno operator.
We wanted to test the kit with and without the air shield that provides a cooler intake charge, but having a big fan blow air at a stationary Jeep really isn't the way to figure out if the air shield makes a difference. | 
Here are the dyno results: we gained a maximum of 6 hp and 4 lb-ft of torque. Looking at dyno runs from past '00-and-later TJs, our baseline was about 10 hp higher than the other 20-30 Jeeps AEM has run in the past, but our final numbers were about the same. | 
The AEM kit comes with a throttle-body spacer. We didn't think it would make much power, so we asked about it and were told that in AEM's testing, the throttle-body spacer added some power. We ran the Brute Force kit with and without the spacer and saw a max gain of 1 hp and 0 lb-ft of torque. |
The Nitty Gritty
While we had a day, a Jeep, and a Dyno, we tested various things. We've been telling people to remove the air horn on the stock airbox for some power increase for some time now. Well, we tested that, too. It turns out that no power was made from that modification. Perhaps the biggest gain is from an improved intake tube. The Airaid kit uses the stock intake tube. For all the dyno charts, results, and a video of Red on the dyno, go to www.jpmagazine.com. If we didn't know better, it sure didn't sound like a six-cylinder Jeep with a stock exhaust while Red was up on the dyno.