If it's the TB I'm thinking it is, it uses a different injector than the dual throttle plate truck TBs.

I'm not sure there were any MPFI intakes for the 2.5. I can only recall TBI applications, including the Fiero.

That being said, an intake could be converted, and MPFI will make getting proper fuel supply a lot easier.

Yes, the FPR should be part of the TB.

As far as the pump max pressure, they can vary, especially depending on age. Most people seem to say max TBI pump pressure is about 20 PSIG, but some say higher. The later 454s would run about 20 PSIG base pressure.

You really need to see what the fuel pressure is doing in boost. It should rise at a rate of at least 1:1 with boost pressure, if it doesn't then you are reducing the delta fuel pressure that will have less flow the higher the boost pressure rises.