I have discovered an interesting phenomenon!!!
 

The 1/2 inch copper pipe cap mod also made the transmission shift smoother when it was cold.The engine would hang at about 1200 rpm while shifting untill I did the pipe cap mod and now the idle will drop to about 900 rpm between shifts.This is easy shifting I know,but the tranny would hang up shifting into every gear untill it was warmed up.Now it goes into gear with no hesitation at all.WHOOO HOO,LIFE IS GOOD.I did use a 3/16 drill instead of 1/4 though.As far as cost and ease to do this is a 10.

What is the copper pipe cap mod?

You use a 1/2 inch copper pipe cap with a 3/16-1/4 inch hole drilled in it to limit the amount of control the IAC valve has over the idle speed.Just drill the hole in the cap,insert it into the hose in front of the IAC and replace the hose.Test the smaller size first with the engine as cold as possible.The 3/16 hole with 18 degree temps gave about 900 rpm.The reason this was created was to control the hanging idle that our cars have when you rev the engine.To give credit where credit is due,this wasn't my idea,someone else must take credit for this one.But it is a great idea.

What are the disadvantages of this?

The cars idle "hangs" because the slower your cars revs down, the less hydrocarbons you release into the air....which is what Ford wanted. I can't say I think this is a great thing to do. Anytime you disturb something of this nature, it can have across the board effects on the way you car runs. Your PCM relies on the IAC for readings that determine many different parameters.
I just opened up my SCT Advantage software, under idle..there are 16 different parameters that are determined by readings in this area alone.Think about that.


Adam

plus whne you down shift it helps keep the rpms up to smooth gear engagment.

I've actually found the opposite to be true.It goes against common sense but so far the tranny shifts smoother both ways.This was an unexpected result of trying to lessen the "hang time"of the engine,but I noticed the difference right away.As far as negatives,i'm watching for these closely during my daily 100 mi.drive to and from work.So far mileage is about the same with no other changes.Cold starts are good with no hesitation.If anything negative shows itself i'll be sure to write about those things also.

Would have been nice to hear that it improved gas milage... ohh well.

The "hang time" is a dashpot function within the PCM. It is adjustable with the correct software. There are a lot of "mods" that are out there that I would be leary of. Some of them, like the J-mod, are reliable because Jerry Wroblewski (the "J" in J-mod) designed the 4R70W for Ford . So some mods I would call researched better than others. :)

Adam