A 1.9td aaz pump without any modification won't work too well.
I am REALLY happy with my 1.9td aaz modified pump though!
average 4.76l/100km-> 51.8usMPG ( during the whole summer 70/30 highway/town driving 115km/h cruising)
Never really tried only highway but I bet it is around 4.3 @115km/h. I think it is better than an e-tdi.
For the performances, a 10mm head with .205 injector makes A3 tdi clutch slip.