Floored,
your question is actually reversed:
how streetable/reliable is my newly rebuilt 2.8L engine to boost?
what kind of components?
did it get bored out? if so, did the piston holes get sleeved?
did the heads get milled? if so, what is your new compression?
did the timing set get retarded? if so, higher boost can be used...
did you use the stock crank? or an aftermarket?
your profile doesn't list which Fiero you have, the '88s timing and ignition are computer controlled, so the ECM will have to be re-mapped and programmed for the hair dryer, some '87s and older still had distributors, so will make minor timing/detonation/knock adjustments somewhat easier.
all of this and many more questions before a more knowledgeable answer.
from Volvos to Saabs, your factory boosts almost double, 12-15 to 23+psi. Stock Grand Nationals run at (I think) 10-12psi, but how big is your waste gate? whose turbo are you using? did you chip your ECU with an aftermarket PROM (Hypertech, JET, etc.)?
big variables... plus your fuel octane, your t-stat operating temp, the climate area you live in ALL play a part too.
if you used good aftermarket components (hyper-eutectic pistons, chrome moly pushrods, double springs and at least a five angle valve job, etc.etc.) a good baseline would be 6-10psi...
(all a part of tech and tune)
...and even if the engine can handle it, do NOT go overboard, or you'll spool it up and fly, and leave the transmission pan and a couple of severed axle shafts laying in the street.
an excellent website for forced air GMs
http://www.t6p.com/index.php
you could also search the web,
in the mid80s Chevy put out a
twin -turbo 2.8L S10 pick-up!
good luck,
hope this helps,
chris
nrt racing