[HiFlow5 0]

My car had been running great for awhile since I installed new heads a few months ago. Now just recently upon start up, it will surge pretty bad then die. But that only happens sometimes, usually after the car is warm. Other times it starts up fine but idles at 1100 rpms, them a moment later drops to 900 and is fine. I've cleaned the IAB and even swapped it with my other mustang and it still does the same thing. Anybody have any clue what is going on here?