Broken petrol cap!
Broken petrol cap!
Not a clue! Try looking at the workshop manual on http://bahamutcars.free.fr/workshop/
I've never done it. But if you are confident enough to try, I'd start with removing the old one, just look at it and see if you can figure it out! (Sorry, I do not have an IS200 handy for reference or I'd check for you!)