Baker, in the various truck clubs that I have been in over the years, one of the clubs actually did a test and used like 10 different "vortex" spacers with a truck on a dyno. they even went as far as to take all 10 of the spacers and install them at the same time. The end result, the truck actually lost power (about 2 hp as I recall) due to adding just the one spacer.
Like was mentioned, the vortex is created (like they state), but as soon as the air comes to a corner, the vortex is destroyed. Now, look at your truck and count the number of turns the intake makes between the throttlebody and the heads. It makes at a minimum of one 90 degree turn and two 180 degree turns. There is no vortex left by the time it hits the cylinders. Now, if you could put a small version of these at say the entrance to the head, then you might get something. Oh wait, there is an intake valve in the way. Guess not much spinning action is going to occur. Might be able to get something if you installed vanes on the valve itself. But, now you are making the valve heavier and limiting the top end RPM of the motor.
