tfsi lack of power

Hello I have recently purchased a b8 2.0 tfsi Quattro and have noticed that there seems to be a distinct lack of power above 5000 rpm, there are no fault codes present and it pulls well up to 5000rpm. I have previously owned a b6 1.8t and the power delivery was much more linear all the way to the red line.
It has 30,000 miles on the clock and has been stood for some time. Prior to me buying it.
I have tried using a couple of tanks of V- power and giving it a good thrash to try and clear it out but there is no improvement.
Does any one have any suggestions on how I could diy diagnose what the cause may be before I pay for it to be plugged in?

Thank you for the offer. I live in the Manchester area.
I am not adversed to paying for plugging it in if thre is no alternative, I am curious to whether there was any way of testing likely components diy?

Thanks for the info guys. I have previously had dv problems wirh my old b6. I think my first job will be to replace the dv as I plan on chipping the car soon so could be two birds with one stone.
Cheers for the graph geoff. The drop in power from 5000 in my car is mush more pronounced than tailing off. More like someone hitched a trailer on the back.