charge motion control deletes

Also called IRMC. They are mounted under your intake. The stock one's have a butterfly valve in each port. The aftermarkets don't have the valve. Some believe they are mostly for emissions. I have no idea what the true purpose of them are. I do know that it lets the motor breath a little better. Mine gave me 6 rwhp and 6 rwtq. Steeda.com has these. You can also buy them predrilled for nitrous nozzles.
 
My guess for their function would be to keep the mixture velocity a little higher, this helps with overall economy, higher vacuum, and crisper throttle response. They'd only get in the way from a high preformance viewpoint though.