When you create something in forge, aim at the object and press X twice. This will open up a screen.
Scroll down to the run time minimum, and set it as high as you can.
This allows fusion coils, powerups, weapons, vehicles, and any other objects to spawn instantly they are taken, moved, or destroyed.
Note: Change the game type setting (or whatever, press C on a turret) to symetric. Then the turret off and another should spawn almost instantly. [thanks bunny brigade]