To answer your questions:
1. No, it will run out of resolution at 350hp (at the flywheel).
2. You can't - it's not a desirable or recommended
MAF to use (too small & lacks resoluton).
The Normal GC8 setting is only for the original Version 5/6
MAF, with the factory airbox and snorkus installed and nothing else.
To run a v3/4
MAF you would need to fully map out a custom airflow curve in the power fc on a dyno.......Not worth the time nor the money - considering Apexi has already done the hard work for the Z32 & Q45 airflow/voltage curves already.
Any
MAF change will still require a re-tune but the basic airflow curve to suit the Z32 (or Q45) is built into the Power FC, tweaks are needed to allow for airflow changes due to cams/compression etc.
Why the resistance in changing to the proven long-term reliable Bosch (Nissan)
MAF's?
Do you have access to a datalogit or other powerfc tuning software, along with a wideband?
Do you understand the
maf airflow/voltage scaling in the powerfc and how it effects your maps?
I have a similar set up to you (read my sig below) and I do all of my own modding/tuning/etc.
A Z32 is the way to go, it has better resolution than the Subaru
Maf's, is far more reliable & it maxes out somewhere around the 550hp (400kw+) mark.