Originally Posted by paul21
If your car feels mostly smooth then random harder jerks at idle, you should reset the car computer by disconnecting the battery for ~30 minutes or something and letting the engine idle for 5 minutes when you start it back up.
If your idle is smooth but causes a lot of vibration in general, then it's the motor mounts.
12B37 increases idle RPM from 700 to 800.
My car was built after the date range for the 12b37 update, but still idles at approximately 680 rpm with the a/c off and in park with my foot off the brake, or 750 rpm foot on the brake in gear with or without the a/c on approximately. At no point is the idle over 800 rpm per the digital tachometer displayed in test mode. Once you take your foot off the brake the rpms increase as the car begins to engage the clutch for 1st gear.