TDI MPG question

[deanogl]

I have a 2003 passat tdi130 sport estate with 80,000 miles on the clock. I feel that my mpg is far too low, especially as it is considerably less than a mates bmw 330d. If I drive on the motorway at 65-70mph in sixth gear and reset the computer I cant get the average to go over 33mpg. When I got the it had a tuning box fitted which I have unplugged as I thought it may be the fault, it made no difference. I have put injector cleaner through it, no difference. Changed the Mass Air Flow sensor, no difference. The fuel and coolant temperature sensors have both been changed and also made no difference. I bought a VCDS 10.6.4 on ebay which seems to work ok. There are no errors stored at all. I checked the Torsion value and found it slightly off so I adjusted the camshaft to bring it to where it should be, still no difference. What else could be bringing my MPG down so much? I have checked all the basics such as tyre pressures and brakes, all fine. When I reset the computer on the motorway to check it was on a 10 mile stretch of flat road with a slight tail wind. I have seen people saying they can get 55mpg if they drive right but the only time I see this is if I am going down hill and just bearly touching the throttle pedal. I bought this car as it was supposed to be good on fuel but when my mates 6 cylinder 3.0 diesel bmw can get 50mpg it makes me want to sell it again. Any help greatly appreciated, Thanks.