http://www.erta.ru/review/chorus-problem_eng.shtml
there ya go, my wifes car has the same prob, you need to get hold of a car audio repair person. look on ebay I found 2 ranging from 85quid to 99 . it is a chip problem and cannot be repaired by yourself :( as I would have done it .
bugger !
Mick, October 2009