This almost falls out of the 'hot rod' categories but is a performance related question.

Obviously, I can buy a cold air intake system for my truck, but since the other half of my genealogy is Scottish, I tend to be a bit of a ----tightwad. Plus most suppliers offerings are in the $3 to $500 bracket for my gas V10 Ford, so the payback mileage period is out of reality. Has anyone built a successful cold air intake system for his EFI vehicle? How successful were you as far as performance and possible fuel savings? How did you build it - that is, materials and a filter? What kind of costs did you incur - and do you feel that it will soon pay for itself?