my car has the same problem. but i have a cam, and it shuts off right after i start it when its ice cold, like sitting over night if i dont blip the throttle a couple times.

surging idle is a huge pain in the ass with mustangs. but any car that starts up has a hard time for a sec to get and stay running.

there are so many things it could be, like mine still bogs and surges when i downshift or dont accel in the gear im in and throw into neutral. its something ive chased around for the longest time, and still happens.

good luck, ill find the bitch of a problem someday, lol