Hi 07HDF150,

Yes, that is right - if you go back to the factory tune but leave on either a 3.25" or the 3.5" AF1, the engine will run lean - do NOT do that. If you go back to a factory tune, then you must also reinstall the factory intake kit.

The other way around that is to order the 3.0" version of the Air Force One - now *that* version of the kit has a small enough cross-section that it does not lean out the engine - but it also does not gain as much power as a 3.25" or the 3.5" versions of the AF1, either.

This is something that affects ALL vehicles, by the way - it's just that it has a more pronounced affect on the newer 3-valve Ford engines since they have a different style of MAF sensor, where it's a "tonsil" style sensor that slides into a tube, instead of the older "traditional" MAF meter that also included a section or air handling tube a few inches long - so the older trucks will go a little bit lean with a good intake kit, but not enough to hurt them - while the newer 3-valve trucks will go much leaner with a good intake kit that really adds significant peak power to the motor.

there are a few kits out there that only add a little bit of power down low, and actually reduce peak power and they do not cause lean conditions, but they also are not worth having due to little power gain down low, and either no gain to an actual loss of actual peak power up top.

Just a quick primer for you, and if you'd like to go over any of this in more detail, please feel free to give us a call, OK?

Thanks for your post!