My first code P0446
 

I had fueled our 98 986 earlier in the day and after a number of 6 mile drives my check engine light came on and when I read the codes I had only one. P0446.
I have cleared the code and will drive the car agin tomorrow and see if it returns.
In checking the forum I found a number of similar issues but some had multiple codes and starting issues. When the cel came on I pulled over and shut the car off. It started immediately. I will check for the A290 service sticker and if it is not there I will upgrade the gas cap. Beyond that does anyone have suggestions of what I need to do. I will update if the light returns.
Ron Jackson

Here is the best thread I know of on the site. If you check his member name? You can find others of his. Good luck. It's kinda like chasing your tail.
Randy

http://forums.pelicanparts.com/boxster-cayman-forum/675334-help-identify-vent-line.html

From what I've been reading, if that's the only code you got, then you can reset and see if it comes back. Sometimes it does not.

If it does, the next step is to blow a shot or two of compressed air through your vent line.

If that doesn't help, come back here.

After close to 1000km the CEL has not returned. The local Porsche dealer tells me my fuel cap 986 201 241 03 is the latest version. There is no service sticker on my trunk lid for A290-update gas cap that I read about on another thread.
Hope this helps anyone who encounters a similar fault code.
Thanks Randy and Bar for your replies.
Ron Jackson