The Blueflame Dp will not fit to the MILLTEK as it was designed to fit as a full 3.00 system and not as an up grade to a cat back.
Be prepared for quite a hefty bill for the ceramic coating and remember the flex will need masking off - although the coaters will normally do this for you.
The efficiency of the thermal wrap is around 20% greater than the ceramic coating and therefore exhaust gas temperatures are greater and hence they flow faster - great news for the TFsSi 's.
It's also important to note that a hotter cat is more efficient than a non coated or wrapped one, again good news especially if a cheaper cat has been manufactured into the DP.
Lastly there is a slight reduction in life expectancy of the part having been wrapped or coated than non wrapped (ironic as that sounds) although were are talking a drop from 20 years to 18 years - not something that will worry most of us.
Sorry last but not least the biggest gain will come from the fact that the bore is 76mm on the BF DP not 70mm which is further reduced to 60mm where it meets the flex joint.
If you need help with the connector pipe between the BF DP and the MILLTEK let me know and I'll sort it for you.
Nige