Issues to look out for, real MPG & remapping

Hi, I currently have an A4 170 quattro which needs replacing this year. I am considering a B7 Passat 2.0tdi - are there any common issues to be aware of?

We have previously owned a 140ps diesel B6, which I thought was underpowered for the size/weight of the car, so considering the bluemotion 140ps and then remapping it to closer to 170ps. Has anybody had any experience of this? and what is the real MPG achieved by a standard car?

Thanks for any assistance/advice!

At 40,000 miles my 140 bluemotion has averaged 53 mpg since new - I keep a log on Excel of all fuel purchased for it and relevant mileage.