My wife loves her TDI, it has plenty of power and if you chip it it will realy go. Many people have to do a clutch upgrade after chipping. The last road trip she went on was to Moragntown WV. and it got 48mpg. Remember her car has an auto-trans. A 5 speed will be 2-3 mpg more than an auto.
BAD FUEL = OLD FUEL. Get your fuel from a station that goes through lots of fuel.
Here is a great site for TDI info.
http://www.tdiclub.com/