Use these to get an idea of how the system works, and how to repair it. The EGR/Thermovalve/Air Injection plumbing is usually the problem with Fiat, and the hardest to understand. These diagrams at least show the flow of the system as it was designed. When doing heavy repairs of your own, try to find vacuum diagrams specific to your car so you don't get into trouble- These are very general, and cover lots of years. See Smog System Maintenence and related articles for explanations.