1) I believe the Stage 2+ would have to get a custom tune done it since OFT tunes do not naturally support CAI/SRIs. OFT is not the greatest when it comes to respond to tickets, so good luck.
2) Per the Knowledge Base and How to from OFT
Stage 2+ Hardware Requirements:
- Aftermarket CAT-LESS header. *Any exhaust modifications after the header is also compatible
- Stock Airbox (with or without aftermarket drop-in panel filter)
- Premium grade fuel
So there's a gray area of what OFT considers premium fuel, but I would run 94 since 91 is the bare minimum for these engines. Remember that OFT tunes are generic and not costumed.
3) Refer to info posted on 2. Again, OFT tunes are generic, the only increase in power, in a more noticeable way would be going EcuTek for each custom performance part of your vehicle. Not saying that OFT is bad, I have it, but you don't extract every possible HP from the supported mods each stage allows. Below for their parameters on each stage.
https://support.openflashtablet.com/...e-requirements