IAC is the easiest to blame so check the hoses and elbow. check all your connections again, including the MAF sensor and any hoses that go to the air intake.
i'd say something happened when putting the new plugs in. Old and worn Spark plug boots can leak electrically causing all kinds of "stalling" issues.
Is it a 4.0 or 4.6L?
The 4.6L have the Coil on plug packs which have an electrical connector on the side. Check those side connectors. Most of mine had the plastic snap piece break off as i was unplugging them for the first time at 118K. Same for the fuel injector snaps. Were the boots dry or cracked? Did you add silicone grease to the boots? Use a good marine grade silicone like 3M for either the 4.0 or 4.6L engines. Add it to the side connectors on the coil packs too. This keeps out moisture and helps the boots go on the plug better. If its a 4.6L, also double check that the fuel injector connectors are back on properly since you more than likely had to disconnect them to get to the coils.
if it keeps wanting to stall, the check engine light will eventually come on and stay on.
when it does, take it to autozone or any other auto parts to the have them read the error codes and then search here for possible solutions.
