Not much you can do to an N/A full stop really. The Audi will seem faster because the turbo gives you a big wallop of torque very low down in a diesel. I'm sure it isn't really as quick unless it is a 4WD one, in which case it will be a lot slower from a roll.
I'm wondering if N/As have the same gearbox as the turbos. If so, doing 72mph in second gear is going to knock your 0-50/60mph down a lot. A weirder option to effectively reduce your ratios might be to fit wheels with a smaller rolling diameter
Other than that, all I can suggest you do, is buy a turbo instead
N/As are all about the looks and (even better) noise without the performance and maintenance costs of the turbo models.