2006 Infiniti G35 RPM

That's normal for some vehicles.

When the engine is fully warmed up and you're driving in the highest gear at highway speed, hold the accelerator perfectly steady, then momentarily tap the brake pedal with your other foot. You should see engine speed increase about 200 rpm, then drop back down one or two seconds later. That tells you the torque converter is locking up for better fuel mileage.