They are at the bottom of the intake manifold, under the throttle bodies, on the crossfire to mix the fuel, kind of like a tornado. Some peolpe have taken them out, others have not. I will be tearing down shortly so I am considering takeing them out if they make a differance. I thought I would ask others.What are swirl plates?
Hmmm...I dunno. Is it the same theory that was tested in this Popular Mechanics article from 2005?They add value in creating a vortex inside the manifold, which keeps the fuel/air charge in a columnar flow. Think of it as a little tornado jumping around from intake port to intake port. But for added high speed flow, you can cut the throat back to increase the volume of air.