98 beetle P1128 code

I received a 98 beetle with check engine light on P1128 code- long term fuel trim too lean, found air pump hose disconnected from air cleaner, after reconnecting will still set code after 10-20 miles of driving. I hear a hissing from the 1/4" vacuum hose that enters the air intake duct under the breather from PCV, but can't seem to find a leak. Anybody have any ideas?