As a guide, my Evo can be driven 'off turbo' at approx 2,900rpm. Anymore than that and the boost guage trys to do a full circle , but then it is pushing out close to 290bhp .
The last standard pre-Evo 16v Integrale I drove (which I think the Q4 engine was based on) was a little higher at around 3,200rpm. I think the Q4 had a lower standard power output to the 16v Integrale (200bhp) by about 10bhp or so, but not sure what effect this would have in comparison on the power delivery.
Out of interest what sort of fuel consumption do you get for the Q4 (worst / best)?