Just wanted to pass on a bit of information about this issue. This may or may not affect 2nd Gen Vibes, but definitely the 1st Gens. My daughters Vibe started experiencing this two weeks ago, and I just now got a chance to get it up on the rack to look the evap system out. Turns out there is an open vent tube coming from the charcoal cannister, that had a spider web with insect cadaver in it.
This blockage caused the system to not allow the system to allow for proper air flow, causing air pressure to "push back" against the filler opening.
Long story short - if you are experiencing this slow fill problem, check for blockages in this open vent tube - at the charcoal cannister. Critters like to make it their home.