what would be the advantage of a 6" intake on my banks sidewinder turbo??? Would it give me more MPG??? POWER???

 

It depends on where the air is coming from, if you just have a 6" tube under the hood it's not gonna do squat.

 

from the turbo it goes from a 3" to 4", then 4" to 6" all the way to the front with a 6637 Napa air filter, i still want to enclose it somehow to get cold air

 

You need to isolate it and get outside air running into it somehow. I ran a temp test not too long ago and underhood temps stay pretty hot even when cruising. With an outside temp of 72*, it was about 140* under the hood at 60mph.