Last night I ran across a thread at ClubTitan's site. It was a long thread---about 238 posts and 29 pages---but it was very interesting. One member apparently had some money to burn and access to his buddy's dyno and did a comparison of various CAI's and included the stock air box with the "Titan mod." Now, there are some variables to take into consideration: his Titan was significantly modified, so performance results may not be the same for a stock Titan, and, obviously, comparing Titans to Pathfinders is sort of like comparing apples to oranges, maybe a little less so if you have a V8 Pathy. He also tested two throttle body spacers.
In his finding, he found that all CAI's had an improvement over the stock box, mostly in the mid to high RPM range. It seems if you are one of those that rarely sees "aggressive" driving conditions, the stock air box is just fine. S&B Intake Systems had the best performing air intake, but, unfortunately, they only have a V8 Pathy system and none for us V6-ers. In second place was Volant (with the ram air scoop) and Injen. He noted the air scoop on the Volant was likely only beneficial on the highway at speeds 70MPH and up and the Volant was the noisier of the two systems. The Volant had better dyno numbers, but it was the Injen that had better performance numbers on the track. In general, all of the aftermarket cold air intake systems did pretty will and were pretty close on the dyno. So, if you read the thread, take from it what you will. The $250 Volant and the Injen PF1959P (polished), which I found for $310, or the Injen PF1959WB (wrinkle black) for $299, are looking much more attractive!
As far as the throttle body spacers, he seemed to feel that if there was any benefit, it was at before the point of where the dyno started reading. If there was any benefit, it was at low RPM, but most who have installed throttle body spacers seem to feel they were a waste of money. Here's the thread if you are interested:
http://www.clubtitan.org/forums/showthread.php?t=13697