The cone should be the same bore and should fit. But just by fitting the cone to a 1.8t will reduce engine performance due to engine heat soak. Go for the extension pipe which takes the cone to behind the bumper where the intake air will be cooler which can extra power. There is a guy on ebay doing a full mk4 induction for around £40 his user ebay name 800bhp I have used items from him a few times.
Nick