I am having trouble because of streatching of texture on a simple object. How not to get that streaching? As you can See its a simple geometry with 2 level of Subsurface and smooth shading. The UV map is simple and dont show any streach. Test material is simple still the render show the streaching at certain areas of the object.
Did you ctrl+a apply scale before doing the unwrap? If not you will end up with a result like this. I just did a quick test and did one without the scale applied and one with the scale applied and you can clearly see the one without the applied scale has the stretching. However the applied scale one looks as how it should considering the texture I used is a low quality image. But here is the example I did with applied and non applied scale and unwrapped and texture applied.