I run the Downey headers on my 90 V6, they seemed to have helped alot, though I have other mods as well, i.e., cold air induction, and ignition upgrade.
A buddy of mine runs the Thorley from Summit on his '92 efi, he seems to like it, he is able to get up to highway speed turning 37" Krawlers on 17" bead lock rims with 5.29 gears.
