So i've been looking at this for a while now.

Do you ever need to increase the iq axis on edc 15?

Surely the SOI and duration is what determines the amount of fuel injected so is there ever a need to adjust these?

As i was bored I changed the x axis up to 70mg/s on a friends fabia (along with a bunch of other maps to account for it) and it doesnt seem to have made any difference that i can see or feel other than fuel request now being 70mg/s.

So even if i go to a bigger turbo and injectors, i should never really need to change the axis data right?

If you want more feul you need more duration.
Its not that simpel to change the axis.
Durations need to be calculated.

For a light tune you dont need to change durations and soi.

Would the axis data effect the mpg readout on the dash?

No. There are other values you need to change so you see properly your MPG on the dash.