If the scoops that you speak of are the pair that fit over the air exhaust grills, I would not recommend using them. The cooling of the engine compartment relies on air underneath the engine to come up and over the powertrain to cool it. The hot air then exits from the air grills. When the car is moving, these over the roof scoops force air down the grills with pressure and prevent venting. Those scoops may impede the natural air flow used to cool the engine. I believe that they are no longer made..
Now if you are referring to the over the roof scoop centered on the deck lid and used on the Indy, IMO that is a better idea.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner 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 "