You can remove the fuel supply manifold, along with the fuel injectors, without unbolting the lower intake manifold. The fuel supply manifold is fastened to the lower intake manifold with the same studs that hold the nuts for the upper intake manifold. The studs require a "reverse torx head" bit (forgot the size).
The best way to free up each of the injectors from the lower intake manifold is to twist back and forth while pulling. Work each one, they will come out easy enough.
How did you determine that an injector is leaking?