I am running the Amsoil by-pss system but do not think you are going to run longer than 5k just because you have a by-pass it is everything to do with the shear of the oil i also run Amsoil 15w40 and still change mine at 5k because i pull a 14k 5er most of the time + it is just smart to. There are a few different setups as far as the oil cap goes but this one Oil Bypass System, Stainless Steel Braided PTFE Lines, Parts and Accessories
as already posted has a different cap depth by about 1/32" it is pushing the filter down more as reported here if i remember right so it is pushing to hard on the filter. I call Amsoil tech line and the told me that there cap is the same as the oem the only way i will be able to tell is when i change the oil and check with the old cap. The main reason to run a by-pass is to clean the oil down to 2 microns where the Ford filter cleans to 20 microns. I think this is a posting by PGreen can't rememder getting to old
See if you can follow this and see why we install bypass filters. The 6.0 injection system uses High Pressure Oil to fire the fuel injectors. This oil is pumped through very small orifices in the injectors at up to 4000 psi. This is what causes the shearing that prevents us from getting extended oil change intervals. That shearing reduces the oil viscosity so that if you try pushing your interval 3x the recommended you will end up with a 20 weight oil. Not a really good idea.
Now, the 6.0 also pumps a lot of oil through the engine. In order to satisfy those oil flow requirements the primary full flow oil filter only filters to 20 microns. That is fairly coarse for the demands of our injectors. A bypass filter takes a smaller flow of oil and filters that oil down to about 2 microns. It basically takes about 10 minutes to filter the amount of oil the 6.0 holds but in continued filtering end up filtering the particulate content of the oil to a particulate that is 10x smaller. If you need to put that in context try sanding a piece of metal with a 150 grit sandpaper and then try it with a 1500 grit and see the difference in wear.
The point is that clean oil is better and that's why you use a bypass filter, not to get the extended milage.