5.0 85 GT

to clean the iac, looking at the car fromt he front, pop the hood and on the drivers side there is a little trianlge looking thing with a electronic sensor on it and a plug

unplug it and unbolt the two small bolts, buy some carb cleaner and spray it in there, you can wipe it out if its dirty, then spray it one more time and let ti air dry, put it back on and bolt it up, tka eit out for a ride, you can reset the battery for good measure, and it should stop that power loss feeling when you let off, did it to my 02 and fixed it, some just block it off to stopt he hangin revs and what not..

1996stang

Just to throw something out there, have your trans filter cleaned/ changed and have your transmission reflushed and maybey even want to have the valve body on your trans checked out to make sure none of the springs or bearings are wore out from shifting (this would be a good time to do some small upgrades to your trans to get firmer/faster shifts also)
Just an Idea that might fix your problem

PistolPete79

i had a prob like that and found out one of my cylinders wasnt firing!

Hangwire

How long have you had the car?

If its for a year to a year and a half or less then you're probably just getting used to the power. I would seriously consider disconnecting your battery for 10 minutes to reset the KAM(Keep Alive Memory). KAM is memory that is learned over time by your computer...it stores things like short and long term fuel trims, idle trims, etc and adjusts to make it run more fuel efficient. Considering you have an auto I think(not positive) what it stores effects how it runs even more since you arent the one doing the shifting, the computer is.

01GTDropTop

Yes its an Auto (going to change my sig)\
Ive done the battery trick.
Ive had it for 3 years actually. I just put on exhaust and gears. It felt great for a few weeks, then "ehh". But it's starting to get cold and whether you are used to it or not, it should "get up and go" when the weather drop to 50s and 60s.
Feels like I'm towing something. Like a big rubber ball underneath my throttle pedal. I dunno.

01GTDropTop

Well, my power is back and then some! I have been debating doing Seafoam for awhile now and finally decided to do it. And all I can say is "WOW!"

My car feels better than ever!

I guess it just needed some laxitive. Haha

The whistling sound has yet to be determined, but not an issue at the moment.

Thanks for all your help guys, I really appreciate it.