Engine revs up and down at idle

[Merccooper]

I’ve been struggling with this for a while. As the title says, the engine revs up and down at idle once it gets warmed up. No issues when in gear.

2007 G35 with the VQ35HR

- revs between about 2200 and 1700 rpms constantly
- no error codes
- only after it is warmed up
- settles down once in gear
- with engine off, disconnected one MAF. Started the car and rpm’s went high, then down then pretty much stalled the engine. Did the same with the other MAF and had the same results.
- did a (home made) smoke test, no leaks.
- cleaned the throttle body’s. Yes, I moved the butterfly’s
- did a relearn several, several times. Other than if the issue resolve, I’m not sure how to tell if the relearn took.

The car has been parked indoors without a battery for about 6 years, although I believe it was having this issue before being parked.

I’m grasping at straws now. Any suggestions would be very much appreciated!!