Piter,

I created a SubD branch to better match your tube shapes. Then I created the precision sections with NURBs using a Circle and the "D" shape profiles. Next I used Blends to tie everything together.

This was just my first attempt, so the process would need some refining to get it to look smoother.

*** Update ***

OK, after experimenting a little more, I think using Loft rather than Blend may give better continuity when connecting the SubD branches to your precision NURBs profiles. With Loft you have control over the profiles, and with careful rotation and positioning of the profile curves you can get reasonable continuity. Of course use as many profile curves as needed to guide the result - I only used three in my example. I would actually Loft the upper two branches past where you need them, then as a last step, Trim the branches to the desired length. Also notice in the bottom image I first Trimmed the SubD upper branches at an angle rather than straight across as in my earlier example.

See bottom image.

I attached the 3DM.

Ed Ferguson