I’ve had this issue since my car was tuned for larger injectors and hybrid turbos. Anytime I shift to neutral and take my foot off the throttle, the rpms drop probably below 500, the engine sounds like it’s about to stall, but then revs back up to about 1k, and then is totally fine. Car runs great so I’ve ignored it. Just wondering if anyone else has that? Car has been pressure tested, and is tight. No codes. Logs look great.

 

Or vacuum leak. The ECU is trying to stabilize when input drops suddenly.

 

^both good answers.

also if you have a lightweight flywheel, I've heard people have had issue with taking foot off throttle and car stumbing or stalling near idle. Tune can be adjusted to compensate for this if both of those solutions don't solve it.

 

how big are your injectors? maybe log and post it here to have a look

 

Seems that the injectors arent calibrated good enough.
I do use bosch 980 ccm and i have no such issues. Idle is like stock.

 

Good idea to do a quality pressure test first, then go from there... I've tuned hundred of cars with those injectors and do not experience that issue...

 

I will retest, but I’ve done a pressure test 3x this year. It’s tight as a drum

 

Ok,
I can raise Idle rpm speed a tad... usually LWFWs cause drama like that but yours is stock...

 

Easy to try: Do an E-Gas calibration.

The procedure I use is with my foot off the gas pedal (and remaining off the pedal through the procedure) with the ignition key off turn the key to the on position.

Leave on for at least 60 seconds. Then turn the key off for at least 10 seconds. Next time the engine is started the calibration is complete.