I don't have a huge desire to run E85. I know it can make power, but don't want to deal with the hassles of getting consistent clean E85 locally. I'll stick with regular 93oct. Also don't have any desire to run water/meth. If I do aux it will be for fuel only.
Yes I would have concerns flowing fuel through a manifold that was only designed to flow air. It will behave different. Without individual EGTs or individual 02s it would be hard to tell if your aux fuel is being properly distributed. I'm sure you can get by with a safeish tune, but without being able to make sure all four cylinders are getting the proper fuel mixture, I'm still hesitant to say single port is a good safe option over a four port.
My goal isn't 350+whp. I want more than what the car has now without ruining the character of the car. This is a fantastic backroad car, but gettting out run by Camrys, Minivans, etc is depressing. Coming from a 375whp S2000 the Fiesta is slow.