okay I figured out how to extrude the cable and give it a twist. Instead of extruding an array of nurbs circles using surfaces>extrude I created an array of 6 sided polygons, combined them and extruded that object with polygon mesh>extrude (with polygon extrude there is a twist option - see image below). The results are quite good, but still not really visible at full shot range. I am thinking now I can create a normal map using the original tubes are the wrap geometry.