Ok, so.

Basically, when I pull to a halt and my engine rpms drop to idle (1000RPM, tuned) the engine will start to hunt/surge. it moves up to 1500, then steadily down to 1000, then up to 1500 and so on so forth a fair few times before finally settling somewhere between 1000 and 1200.

The amount of times it will hunt before settling varies from twice to like 13 times, sometimes more. and it does not hunt on cold start unless i touch the throttle.

This problem began after I changed the following things on the engine all at once:

Gearbox
Exedy 9.5lb Flywheel
Exedy Stage 1 Clutch
Skunk2 Intake Manifold
Injen CAI
PCV Valve
Hondata IM Gasket

Things I've tried to fix the issue:

-Going over all the vacuum lines/injectors/manifold/brake booster/throttle/charcoal canister with carby cleaner and found no vacuum leaks.

-Reset the ECU.

-Cleaned out the IACV very thoroughly with carby cleaner.

-Cleaned out the FITV very thoroughly with carby cleaner and wound it all the way back in.

-Cleaned the throttle body very thoroughly with carby cleaner.

All I can think of now is air trapped in the cooling system somewhere tricky, faulty PCV valve (even though it's a new one it's not OEM), or is there any way that these parts could mess with the tuning?

The car is a '95 DC2 B18C2 OBD1 w/ Hondata S300.

Are any of these things more common then not? Has anyone else had this issue?

Any and all input is very welcome.