With DBW, ECU will force the idle rpm at 800rpm.
CCU only sends the A/C ON request to the FCU.
FCU controls the rad, eng bay (if available) and the condenser fans.
It also sends A/C ON request to the ECU based on other sensor inputs.
ECU is the one controlling the A/C Comp. CL.

While A/C operation increases the Eng/Elec load, the target idle rpm doesn't change so ECU will react to the increased load and force the idle rpm to 800rpm.
With DBW, there is no EACV or FIV so mainly achieved by the TH control.

You may want checking the accuracy of your rpm/tacho gauge.
By now, many NSX are showing at least 50rpm offset against the real rpm signal.
More than 200rpm difference at the idle region is rare but there are several examples reported.
You can get the rpm signal from the tiny pickup connector at the right side of the Eng bay.
It's 6cyl so when at 800rpm, it's 40Hz.

Please read the error code regardless of whether you have seen the CEL or not.
There are several modes that require multiple drive cycles before triggering the CEL so you may have stored some codes without the CEL.

Also, as you reported that the locking paint was already missing, did you check the base idle rpm?
If too much air bypassed through the screw port, DBW can't do much.

If none of the above, you'll need checking for sensor readings, air leakage, etc.
Hope it's not AT -> MT converted.


Kaz