You could make it yourself sure, but how long would it last? If you get one from Dougie then I bet it would never crack, if you weld it then I bet it would crack, I bet your merge collector wouldn't flow as well either and your flanges would be warped. If you want a quality manifold that performs better than a log but don't have to worry about cracking then the Symtec Race manifold is the way to go. If you want to try your hand at making one and are prepared to loose around 500 bucks worth of flanges, piping, and welding material(not counting the welder) then go for it!