Loud Noise from area around gas cap

[HammerESQ]

I've got an interesting issue with my 2000 Boxster S.....

There is a loud 'whine' noise coming from the gas cap area. I have traced it down to a line that connects to the Carbon Canister Vent Valve housing.

I placed my finger over the line, and it's pulling a vacuum, but the noise in unbearable. I'm assuming it's the Carbon Canister Vent Valve, but I'm not sure, and would like others opinions before I start spending money.

Has anyone seen an issue like this before?

Thanks!