Are you reusing the original throttle body? If so, did you clean the throttle bore just behind the throttle blades, where they close? Carbon will build up there and cause hesitation and stalling at idle. It only takes a small amount to cause it. I usually take a cloth with some carb cleaner and wipe it out throughly.
Check the idle voltage specs in your shop manual on the throttle position sensor. The 5.0 Mustangs had to be set just right (and could be rotated a few degrees) to get a decent idle (voltage reading). Use a modern high impedence volt meter so you won't burn out your ECU.
I'd also double check the IAC for proper operation. Considering the quality of parts coming over the counter these days, just because something is new doesn't mean it works properly.
Replaced the 2nd cam, (Comp 35-512-8) with the original roller cam I removed from the eng before I rebuilt it. Truck now runs perfect! Idles and does not stall when you come to a stop light. Thanks Art
I would like to resurrect this thread with a question. When you had the camshaft issue, did you use the stock roller camshaft with the standard 302 firing order or was it the 94-96 F150/96-2001 Explorer camshaft with the HO firing order?