Hello Tim, I'm sorry but with the use of blender I am at the step -1. I tried to do something but for now, I only obtained to do some images, not very realistic.
The models have been created such as the Tiny turbos series, using official parts and the unofficial mentioned in the introduction.
I know it's a big job, but have you tried to import into blender just the piece that gives you problems? Taking a few attempts with other constructions (I use LeoCAD for this purpose), I saw that there is some difference between import many pieces together or one at a time.
To get the pieces smooth, without modifying the mesh, you can try to apply smooth to the surface you want to improve, leaving the flat where the surface is flat or do you want a sharp edge. Be careful because if you apply to the whole piece, or to the entire model you will "lose" all the edges.
The models have been created such as the Tiny turbos series, using official parts and the unofficial mentioned in the introduction.
I know it's a big job, but have you tried to import into blender just the piece that gives you problems? Taking a few attempts with other constructions (I use LeoCAD for this purpose), I saw that there is some difference between import many pieces together or one at a time.
To get the pieces smooth, without modifying the mesh, you can try to apply smooth to the surface you want to improve, leaving the flat where the surface is flat or do you want a sharp edge. Be careful because if you apply to the whole piece, or to the entire model you will "lose" all the edges.