On the Audi model I have undesirable surface artifacts that detract from the fit and finish of the model. I have noticed that these are often created by the joining of two curves with radical forms for the purpose of curve networking to create a surface. The infill panel above the wheel well.
Watch these vids. https://www.youtube.com/channel/UCrMbLKSTzacxHoMvE_bYHNQ You’re not going to get smooth surfaces using network surf and 6 sided surfaces.