Hi guys I need some help/opinions. Just bought an 2009 M5 with 70K miles, I noticed that after the vehicle is warmed up, when I shut off the vehicle and restart it, the idle will surge between 600-900 RPM until I drive it. Then it idles perfect until the next warm start. Cold start it's fine no surges. Brought it in to the dealer and they say it's normal for a V10 to surge. No fault codes in any modules. I only have full RPI exhaust for mods. I have seen it on an 06 M5 but not as bad as mine. Any thoughts on what it could be or is it normal? Thanks in advance.