I would like to try building my own intake. Lots of people do it for bent engines, inline would be easier. Make cardboard and tape pattern using the same shapes you wish to cut from sheet aluminum. cut taped corners to separate patterns, trace and cutout. Bend as needed, weld together. Finish with flanges cut from 3/8 wrought aluminum plate and some machining. Material cost less than $100, maybe free depending on what materials I have on hand.
I know easier said than done but does not seem too difficult.
