If you turbo the 2.8L the reprogramming of the timing tables for boost and vacuum in the ECM prom and the use of a 2 BAR MAP sensor is mandatory. A knock sensor is also recommended but you will need the 85 Fiero V6 ECM, an ESC module and a knock sensor. There is a switch in the 85 V6 program for turning on the knock sensor. You might be able to get close on the fueling with injector and fuel pressure adjustments but spark timing is very critical. With boost, excessive advance that you will get in the stock V6 timing table program will blow the engine up in a short while.
If you do the job right, the increase in performance will be significant.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "