Connects to fuel rail on left side of engine. Then it connects to the fuel line that runs back to tank. Problem is that there is some type of filter, check valve, in between (it looks round approx. 2.5" in diameter, the rubber gas line connects to it). I can't find any reference to this part in my tech guide. It only shows the line without this part. I contacted a local jag. dealership and they couldn't tell me what it is as their book doesn't show either. My Jag is a 2000 s-type with the 4.0 engine. Any help would be greatly appreciated!