Hi Penny,
There's no easy answer to this one.
In general, "Faint" has little impact- however that's not always the case.
We were recently considering a Fancy Intense Yellow graded "Faint" by GIA that should have been graded "Medium Blue" in my opinion.
Sometimes Faint has virtually no effect.
The stone in question really changed appearance in daylight.
Its a case by case basis.