Not sure if the injectors can be cleaned, everyone always just seems to replace them on the forums.

That is expensive though; brand new injectors can be had for £150-250. Fitting isn;t hard and coding is simple for a garage. Secondhand injectors will get him out of trouble otherwise, they go for £50.

http://www.ebay.co.uk/itm/BMW-DIESEL...item19fac06678
http://www.ebay.co.uk/itm/BMW-330d-3...item3ce6a4e57a