Ok I will post two strong Theories on why I think the Vahi might, or might not be the famed "Mask of Light."
Mask Of Light Isn't Vahi: Well, way back when the first comic came out, Matoro referred to the toa's masks[kanohi.] as GREAT MASKS OF POWER. And He said that They were on places on the island that no TOHUNGA could reach, only Toa. Now, there has been some people thinking Takua MIGHT be the 7th Toa, the Toa of Light. And it has been speculated that Takua finds the mask and weilds it to become the Toa of Light. But the Vahi is Called the GREAT mask of Time. and No Tohunga can attain great masks. So if Takua gets the Mask of light, and the vahi is the Great mask of Time. That means that the Vahi can't be the Mask Of Light.
Mask Of Light is the Vahi: On the bus rides to and from cross country meets, I get really bored. I don't wanna do my homework on the bus, and I don't wanna bring my GBA for fear of losing it, [My 7th grade science teacher is the Cross Country coach.] So I like to ask My Coach really tought questions about Time and Space. and while thinking of good questions I remembed about the Bionicle and the Vahi. so I asked him if it was possible to slow down time. And He said once that Albert Einstien said that it was possible to slow down TIME if you are moving at the speed of LIGHT. So, Basically, The Mask of Light would be a Kakama that has reached unattainable speeds. But While moving so fast, with the Vahi[Mask of Time.] Your opponents would see you as one second ago. because at the distance of how far away you are, it takes a amount of time for that vision to reach your eyes. [a little off topic.]: You people may have noticed, that people have been saying that with the Kakamanuva, you can go through solid objects, If you tried that with the Vahi, you'd either Kill yourself and the object that you collided into, or you'd barely pass through them. just a note to those who plan on fighting bohrok with a vahi.