Depends on the VW - they wouldn't do jack for my 1960 panel
I have doubts about some of the cold air intakes I've seen, which consist of a long plastic tube leading to the fenderwell. My limited hydraulics knowlege sez there would be serious flow restriction in a tube that long.
I have a K&N on my 911. I just upgraded to a much larger version - this one has about 3x the surface area of the old one - and my gas mileage improved significantly; I think the original baby one was too restrictive.
Do a search thru the archives - lots of opinions on these.