1) 16G, 18G, 20G, run more efficiently at over 20-21psi, I wouldn't bother upgrade to a 'G' turbo & run it under 20psi.
2) you're going to need bigger injectors absolute minimum of 650cc/min and better intercooler.
Also factory-calibrated Mustang dynos typically read lower than most others, the dyno operator has jacked with the settings if it reads high. There's a semi-local Mustang dyno here that reads high because most of their customers are Porsche owners 'expecting' to get what they paid for.
For custom tuned STG2 to come out @ '216whp and 225.9 wtq' you were on a standard low reading Mustang dyno.