I did some testing with factory Ford idle valves this week.
The first 2 I tested did not work properly. These 2 had a small spring inside holding them open at idle and they were very noisy.
When vacuum was applied, they sort of worked, but were not consistent. On a boosted application, the default open valve position was unacceptable to say the least.
After lots of searching, I found a Ford idle valve that works exactly the way it should and operates very quietly.
Go to a scrap yard and pull one from a 1987 Ford Mustang LX or order it from your local auto parts store.
For those getting frustrated trying to find one that works, This one does!
No one to my knowledge has posted a part number for a compatable Fidle valve.
The one I have here has no internal spring and is made by Borg Warner.
The part number is BWD21762.
Hope this helps someone.