For a 98 Boxster, I think the same part was used from 98 to 04.
I'm looking for the fuel tank pressure sensor. It is a little sensor in the area underneath the battery.
It has a plug-on connector with 3 wires, and a barbed hose fitting. It is held down with a single screw.
It should be real easy to get to. I can send a pic if you want. It's small and will fit into a little priority mail box.
Let me know if anyone has one to sell.
Thanks!
Dave