Begin by removing the plenum box clips found along the edge of the two box halves. These clips are unique fasteners that require a dedicated pliers to remove. They might be able to be pried off with a screwdriver, but damage to the box could easily result. Classic Auto Air's plenum clip pliers came from CraftsmanTM, so locating the right tool for the job shouldn't be difficult. Take care not to lose the clips, because finding new ones will be a chore.