You don't have to have a swirl pot, unless you do "spirited driving"!!
The std outlet if 1/2" or over would be fine, if there is also a return line.
The easiest way would be to fit the injection tank though, piping is easy and can use opa flexy pipe to make easier.
I am not sure if the P100 is the same tank as a hatch/saloon etc, but does not have to be cossie just injection 2L ghia etc, xr4i xr4x4.
tabetha