Well considering that number you posted is borderline useless without the compressor wheel and exhaust turbine wheel sizes it is impossible to say. A/R Is a ratio of turbine housing cross section area compared to the size of the turbocharger.
#2 on this page
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html#b
If its a very small turbo that A/R may not be too bad, Though it most likely is too large of an exhaust housing.
Stock injectors have nothing to do with spooling or supporting a turbocharger.
Fuel injectors are proportional to power level. You need X fuel to mix with Y air to make Z Horsepower.
If you take the size of the injector in CC's, subtract 50 the number your left with should be a
guideline of the power they can support on a 7M. Example 550's are good to
about 500 WHEEL horsepower. Again This is
APPROXIMATE and any car should be tuned on a dyno with proper equipment and your results may and will vary.
Find out the diameter of the small and large side of the compressor and exhaust wheels and then we can tell you how much power to expect. Or find out the model of turbo and post that. Otherwise that A/R Number is useless.