Does the probe mount on top of the manifold or on the side.

 

HI!... On the 5.4's it seems that #5 cylinder is the one that runs the leanest most of the time. That would be the front cylinder on the driver's side. You need to drill a hole in the manifold and tap it for the probe right next to the #5 exhaust port. If you have headers it would be in the #5 primary tube next to the exhaust port by the head. Headers you will have to weld in a bung.