Same story with my 2000 V10. But it was complicated by a wrong K&N filter. Thanks to Lordco in Penticton British Co.lumbia for selling me a K&N filter, labeled for a 5 ltr Mustang...that I returned only to have them insist it was the same for the V10, dust was getting by the seal and dusting everything beyond. The IAC has a little piston exposed to the airflow. It got gummed up and slowed and finally stopped the IAC from operating.