Hi guys, first time actually posting on here. I usually browse only, but I have an annoying issue with my G.

2012 G37xS, 136,xxx Km.
I have had an SES light on and some (surges/hesitation?) while driving. Not too noticeable, but definitely there. My mechanic told me to update my ecu from the dealer, as there was a tsb update out. So I got it done yesterday and the SES light is off, and the P0106 code is gone.

However, my rpms at idle in drive (when stopped at a red or in my driveway) seem to stay right at or slightly below 500rpms. Turn the ac on, it fluctuates with some vibrations/clunking in the car. In P, the idle is steady 650~. However, the ac makes it fluctuate still. Its on medium, not like Im blasting it.

I would really appreciate if anyone could tell me if this is a big issue, and why this could be happening. (Couldnt attach a video for some reason, but the fluctuations are around 1-150 rpms up or down.) Not wildly erratic, but moving nonetheless.