One major factor that plays a role in your injector size is the lowest air/fuel ratio you intend to run. I have heard different opinions but very close to if not in the 12:1 range on wide open throttle seems to be where you want to side, so you will need injectors capable of maintaining that kind of ratio at the max boost level you intend to run, the stock wot ratio for the fiero is about 12:1 if I recall correctly and I believe that is partly a safety measure since there was no stock knock sensor installed, I have read however that it maybe a bit two low for optimal turbo performance given that two much and two little fuel can cause power loss and destruction. Whatever you side with, it will definately affect the required outflow of the injector
I would consider the injector range used on the Syclone and Typhoon which I don't believe requires an injector change to get into or just above the 300 hp range. In this area I don't believe considerable excess above what you really need will be a safe error because to large an injector may be difficult to control at low rpm and idle on a relatively small engine.
If you have a source to modify your chip, have them increase the amount of timing retard at the higher temperatures to avoid the detonation in the summer. If your current engine management is working well I would concentrate on using it and further optimizing it to reach the goals set as opposed to starting fresh with a new managment system, but that's my opinion.
