If you are running r134 in an originally r12 system that could be causing lower performance. I don't know what came with a '94 though. In any case, this could be a clue to why your AC has lower performance, assuming that it does.
@dogstar
Do you think you successfully got yours back to stock and are simply wanting more or do you think your 80s AC is performing worse than stock?
I'd guess that my 80s AC is currently performing at, or near, stock/original capabilities and I don't see the need to improve it. The temps...
The AC in my '97 1FZFE works really well for all passengers though it's just front AC and there is no secondary/rear unit. Summers in our area (South Eastern US) are hot and humid and driving without AC is pretty uncomfortable, esp. with a front engine and all of the radiant firewall/floor...