As far as I know it's just there to "hold onto" any "left over" gasoline vapors that would otherwise be vented into the air.
Also, as far as I know, your engine doesn't know, or care, if it's attached or not.
Meaning as far as any engine problems go, there or not, it's not the cause.
Just take a page from my former young and clueless Honda days, just leave it in there and paint it fire engine red.
That way it will not only pass emissions, but will add like 5-6 HP as well.
