Intake Manifold Runner Control. They are butterflies in half of the intake runners. They open above like 3-3200rpm. Its helps with bottom end torque. The plates sit in between the lower intake and the heads. The injectors only spray down the primary because its always open. The secondary runner is where the butterflies are and they get caked up with oil from the pcv system. Some ties they eve get stuck closed which really hurts power.

Not to mention all the crap on them will hurt air flow. I would sea foam the whole thing. then pull it apart and clean the imrc's s everything gets cleaned. You may still want to pull the top off the intake a clean that also while its all apart. It's a easy job just takes a little time.

I would visit SVTPerformance.com and go to the sn95 forum they have tons of info stickied.