True but doubt its much at all maybe 2-5bhp. Obviously more responsive though. Id still say defo get a fmic though.
FMIC is not even a stage 2 requirement, only real need for FMIC is track days, under normal driving and just quick strip runs, it will not really benifit you. On the track with all that heat under the bonnet things will start to take a different toll, which is were the performance will hit a decline.
It's all down to preference, do you want it for looks or a track day toy?
Plus remember the negatives of the IC, putting a bigger IC on will cause more restrcition than in a small IC (just because its bigger, does not make it better), which is where you need to weigh the pro's and cons of what the temperture of air is in the system vs ambient temperture outside to result in gains (if there are any or if under certain conditions). Then the climate in UK, only time the IC really plays a roll is in the summer were it's more than enough, whilst autumn ands winter its not needed due to the cool/cold air and it's density, which brings it back to trackday or just looks. Then there is other pointers to remember, what route are you taking in the bay, such as the same way as before ot over the rocker to accomadate the IC (which brings more heat into the equation), then there is the question about piping, you sticking to 50mm or going bigger, bigger piping and longer runs result in more lag... Then are you going to wrap it up to reduce heat etc...
Not having a dig, but its down to what you want, whether for looks, or no real need to trackdays.