Did the throttle body bump stop mod took about 10 minutes with a die grinder and carbide cutting tool, but when I went to put the SLP bellow on I noticed a black smooth piece of plastic fell out bout the shape of a funnel if you cut the small end off. It probably helped smooth the air comin in but the outlet too it was smaller then the inlet to the throttle body. I was probably losin 10 to 15% or more of airflow. Made a pretty noticable difference with that removed plus grindin the bump stop down. Not sure why anybody woulda stuck that in there.