Dealer re-set the default rpm value too high!?

[autoque]

While I was in the service center, the tech has re-set the default (stationary, ignition on) value of rpm from around 600 to about 720, saying it's the engine's optimal operating rpm.

But after the re-set, I can feel more vibration coming from the steering wheel, and when I turn on the air conditioner, the rpm goes up to 900 rpm but the vibration lessens.

Can they just play with the default rpm value like that? I thought there was a factory spec rpm that's recommended for the 3.0 gasoline engine.

I'm afriad when I ask to tune down to the default rpm again, they won't know what value it's supposed to be.

That's too bad 'cause higher rpm while stationary must translate to more fuel consumption. And this vibrating steering wheel causes fatigue much sooner.