Uh hum, 737-200's, Potomac River etc... We are talking about a modern a/c, B717 and modern motors BR715.
Watchdog is on the right track. The FADEC system is constantly comparing back it's inlet pressures to the a/c probe.
If it's out of whack then the pilot is informed and he can select N1 Mode.
Then who needs a chart? The little man in the FADEC is doing that calculation far quicker than I could do with 10 hand a slide rule!