BP is quite correct. You MUST reach a limit to access the engine correctly. Usually 100%TQ. Make sure the heater and anti-ice are off as well and set 29.92 on the altimetre.
Remember, when you read the chart you are looking for the torque percentile that the engine should AT LEAST produce.
If you are pulling 100% TQ and the chart plots out at 85% TQ, then the engine is actually producing MORE power than spec.
Therefore a +15 engine.