I am also looking into a kind of similar problem on my 04 F150 5.0 A/T truck. I get very intermittent idle issues when coming to a stop. The idle begins dropping rapidly and it stalls. fordfuelinjection.com reveals that if there is a loss in VSS signal to the PCM, the IAC slams shut and it wont idle. it happens usually 3-4 times almost every day but its random and most of the time it idles and decells just fine. I also find that I have to hold the throttle wide open to restart it faster. it will restart but cranks longer at closed throttle. I scanned the truck today with a snap-on handheld and had an intermittent code for the VSS CKT failure cleared it, did a couple of other minor repairs and it did not return. I have recently replaced all the vacuum lines, PCM relay, t-stat back to factory set temp, adj TPS, cleaned throttle body and EGR ports, Reset base idle, and timing back to OEM spec, I also replaced the PCM for another issue it had. it fixed almost all my drivability problems except this idle curse. I also figured out that the replacement engine done by the previous owner has the wrong cam for this PCM (old firing order) and I am wondering if this also is a possible cause. I am trying to get it back to base factory tune or a starting point.