Lately i have noticed that my truck's idle has been dipping severely immediately after start. Today it stalled completely for the first time. If i give it a little throttle it is fine. I cannot decide if it is a vac leak or if my IAC is not adjusting quickly enough. I have not done any diagnostics yet but i decided to post it here to see if you all have any suggestions...

it is an '03 king Ranch with the 5.4L

 

If it's a vacummleak you will also have a check engine light with codes p0171 and p0174 it's most likely your iac I would try cleaning your throttle body with throttle body cleaner, just remove your air filter hose and with the engine running give it a little gas and spray burst all around the throttle plate