EVAP very small leaks haunt my dreams!
We had one on a Silverado that was a nightmare to try and track down. We did smoke tests and had the truck a week. (Absolutely had to pass the emission test to renew the plate sticker)
Turned out to be a slight crack in one of the plastic connectors attached to one of the hoses and it was only when the tank was under the highest pressure it would leak and set the CEL but minor pressure and normally it was sealed up pretty decently and would be fine.