No adjustment as it's a hydraulic clutch so the only way is for you to compare it with another car and see what you think but other than that its gearbox removal and physically assess the condition of the clutch and flywheel.
That may sound daunting but to take a gearbox out of an IS220 is not a big job at all, I did my first clutch replacement on one in about 3 hours so someone who has done a fair few could do it in about 2 I would say