This is quite confusing as i've spoken with BMW parts departmen and the have told me the DPF or particle filter is the part with the square flanges on and the part number i quoted was matched up.

If you look online using the BMW parts catalogue it does list both parts as a particulate filter but one as the primary CAT/Filter so i'm confused.

Look in the garage management section under the heading technical links for the BMW parts catalogue.

Also the internal of the rectangle box does look more like a DPF than a CAT if you look at the picture on BM Catalysts.

thanks
lee

p.s
either way i've found the blocked part.