I can't tell you if the HiFlo comes with the o rings or not. I have not used a HiFlo filter and I have an 06 anyway. Here are a couple of threads that talk about filters that will fit your 400. Both list two different HiFlo numbers so it looks like both will fit.
My guess is no. The OEM filter for the 03-06 does not include the o-rings. When you look at the parts fiche the o'rings have separate part numbers from the filter. For the 07+ models the parts fiche also list the o'rings with a separate part number so I suspect they are also not included with the filter.
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