After looking at tuning a FOcus diesel I found that a remap was the best investment, someone spent some money on looking a turbos, injectors etc but on the Focus it was a waste of money. On my Golf i've settled for a remap, VAGS do respond well to tunning but £ for bhp the remap is the most cost effective route along with a panel filter.Tunning diesel moves the torque higher up and defeats the object of owning one. Also I think the Golf cannot put the power down very well and the clutch struggles.