Two thoughts:
Ford had a TSB for this where they would do one of two things...they would put a 6 inch jumper harness in the salt and pepper shakers, claiming that they were perhaps too tight resulting in a bad connection. IMHO this is perhaps not the best idea because you are adding two new connectors to the mix and thus two new potential sources of problems. I took mine out of the harness I am working with.
The other thing I know Ford used to do is put the IAB spacer in to allow for a little adjustment. If you go to a pick-n-pull salvage yard and paroose the Ford section, you might find one accompanied by a little yellow sticker somewhere under the hood. These help to get a little more air in and they are adjustable. Should be a Ford service part availiable from the dealer...they have a Ford p/n on them.