Question about TBI IAC on 87' 454

[AusTx68]

I did a complete stock rebuild of my 454, broke in my cam then realized it wouldn't idle. If I gave it a little gas it would start and run fine. I pulled my IAC and noticed the pindle was extended. I pushed it back in and reinstalled it. The motor started fine and idled. Over the next 1 1/2 days the idle got worse and eventually stopped. I pulled the IAC again, pushed in the pindle and it idle. I drove it, parked and it wouldn't idle.

Now here's the confusing part. I decided to unplug the IAC. Started the truck and it fired right up. Took it for a drive and it runs like a champ. Plenty of power, no hesitation (previously hesitated), strong idle but slightly higher. Not annoyingly high. So I'm wondering why it runs so good with the IAC disconnected. Does it serve a purpose at engine speeds above idle? I figured my IAC is out so I ordered a new one. Just wondered how long I can drive it unplugged.