Well, perhaps do a Power Assurance Check.
If the PAC is passed the performance charts should be valid.
Easiest way to think about the PAC chart is that it is a paper engine to compare against what your engine is doing.
If your engine is better you will have a power margin available.
Does this make any sense at all?
If your engine is below spec you want to find out why. Internal engine damage? Leaking bleed valve, dirty compressor.( in one case the problem was the wrong torque gauge… took a long time to find that one.)