Here is a picture of the double return spring setup as viewed between the intake runners for #1 and #2:
Here you can see extra spring on the right:
Here is the view from the flywheel side of the motor. The bell crank lever that the 2nd spring attaches to is different than earlier motors. Instead of being one flat piece, it looks like a "hangman" symbol or for you mechanical engineering types, it looks like a the symbol for torque (Gamma) only backwards.
I looked in the PET tonight and according to the that, the single springs were used up to '85 and the double springs were used from '86. That doesn't jibe with the single spring '89 motor I have or with Ralph's '88.
-Chris