For something like that I would consider metal shaping the pieces..make a hammer form and strech and shrink the metal until you have the right shape..make 2 halves and weld them together for a finished tube..Only way I know in some kind of metal that is that thin..if it is on the intake side the material does not need to be all that thick..maybe even 20 gauge would do the job..
The JD2 which I have does fine for the structural stuff up to 2" like for chassis pieces..and can be used for header tubes as well..anything over 2" well that is another story..
Just look at what you need to do and give it some thought and it will come clear just what kind of technique to use..
If I were to make intake tubes for the same car over and over I may even consider fiberglass as we do use plastic these days for something like that and that may be a bit easier to do..
I have tried most all of it and now do what is known to work..