Give him time. If you are gentle and patient he'll come around.
My Nago baby, my first male, never outgrew his huffing as I call it.
The first time I held him after he was shipped to me, he gave a loud close-mouth hiss, which I call a huff because his mouth is closed. He was just terrified of me and was sure I was going to eat him or worse, and wanted me to know just how dangerous an 11" long snake could be.
Over the course of a few months, he learned that huffing was not going to make me stop holding him a couple of times a week. But he still kept trying to convince me he could mess me up if he had to.
After about 6 months, I noticed an interesting thing. Nago it seems had worked out being held with huffing, and decided he was supposed to huff when he was picked up. He'd forget to do it sometimes, and only after I had him picked up and was holding him, he'd suddenly remember and huff at me. I'd laugh.
Now, even though he's been here almost 18 months, he still huffs every time I pick him up. He's never bitten or even snapped, but he's convinced you have to huff when you get picked up.
Gale