I had the 001089 fault code keep coming back all the time. Had a new evap valve (06E906517A) fitted which is usually supposed to cure it, but it didn't work. So I got the charcoal canister (1K0201801E) replaced and so far that seems to have solved the problem. I did need a new piece of pipework (1K02021160BG) for the canister as the latest version has been revised.