Intermittent Idle Surge

I have a 2002 F-250 with a 5.4 engine 4x4 with an intermittent idle surge after starting it up. It started to do this 2 months after I bought it from the dealership. It only does it when I first start it up in the morning. I back up out of my garage and then the idle surges up and down. I just put it in neutral and rev it up and it comes right out of it. The dealer replaced the air bypass valve, replaced the computer, and did a diagnostic scan, but doesn't show any fault codes. It can go 2-3 weeks before doing it again. This is driving me bonkers. I want to figure this out while it is in warranty.

Mine's doing it too. Just as you said, when it's cold. I just read maybe the Idle Air Control Valve. I'll keep looking.