cold air induction and high flow filters

Hi all, could anyone tell me if there is a cold air intake for a vy v6 that is similar to that of the original and how much differance does a high flow filter make to fuel economy eg: K&N, BMC?
and one last thing i seem to use more fuel with cruize control on than just using the old foot??? can any one give me a reason for this.....

cheers

i've heard many comments in regards to high flo air filters ie k&n, the oil actually gets on the a/f wires and inturn leans out the motor due to incorrect reading from the metre.