mustangworld did have an article on how-to install the prochamber, but its not on their site anymore (?)
I have the article saved to my PC, but it's probably not appropriate to post the whole thing.
Here are the install tips from the article:
Install tips:
1) When removing an H-pipe, careful not to bang up the oxygen sensors on the chassis. We recommend removing the O2 sensors while the h-pipe is still up on the stang.
2) The passenger side header uses a gasket and flange, you may need to order a few extra gaskets for constant removal / installation.
3) When installing the passenger side gasket, use two small rubber bands at the ends to hold it in place, this will make installing the h-pipe much easier. The small rubber bands will naturally "burn up" (while driving) and you'll be left with the gasket in place. The stock metal gasket is barbed on one bolt side and stays in place by itself.
4) The passenger side header uses two bolt studs that may "back out" as you are removing an h-pipe. If this happens, you'll need a "stud socket" to re-tighten the stud(s) back into the header. Eventually these studs will get loose and you can just screw it into the header with your fingers no problem. The driver side header (on the 4.6L) uses a traditional gasket-less ball flange.