http://www.ross-tech.com/vag-com/cars/fuel-trim.html
"Mult" mean multiplicative trim, which is addressing an imbalance at all engine speeds. The malfunction (e.g. clogged injector) becomes more severe at increased RPM. For multiplicative adaptation values, there is a percentage change in injection timing. This change is dependent on the basic injection timing.
seems to say its your injectors, go down to your local halfords or motorsave ect and buy an injector cleaner/fuel treatment, theres ones for petrol cars and diesels so make sur you get the right one.
cost 5 to 10 pounds
follow instructions on the bottle but normaly its add to full tank of fuel. do that and then reset your fault code, see if it comes back.
car will run a better on it aswell.
thats all i can think of, iv searched the 2 fault code sites i know of but the codes not on any but i did find the above link