basically there is a limit to the amount of fuel the standard mfi unit can give, this will limit the amount of bhp you can run with supporting mods. There are three ways around this:

1)change to efi (costly and some would prefer not too)

2)have metering unit modified by the likes of m.a.d and jamsport etc (great results)

3)run fith injector kit (mf2 fully mappable is a great hassel free upgrade also with just as good results as the above.)

Really if you want big power then you need to think about this if not you will be fine, if your tuner tells you the next stage is more fuel then the above things will help you achieve this.