My T6 Kombi is a euro 5, 180 bi, with a manual box. As it is a leisure vehicle I don't carry loads of weight around on a day to day basis. However I do tow the kids sailing boats and or a RIB about. Can't comment on tyres yet as only had her a couple of months. However, regularly get low 40's when towing, with a best non-tow of 47mpg.
I prefer to have the power and not use it, than need it and not have it.
I've had a number of Audi's that I have remapped and whilst it does add power, but more noticeably it does improve fuel economy. Definitely looking at a 245 remap, at least it'll come closer to the 272 A6 that I got rid of to buy the van. In the words of a certain Mr Clarkson, POWER!!!!!!!!