Just did an engine swap and for some reason I am getting engine rpm surge issues.
Unplugged the IACV and it goes back to nice and calm. Plug it back in and it still acts polite - turn the car off and restart and we go back in a circle.

Ill clean it soon, maybe swap it for the IACV from the other engine. Any likely causes? Air in the coolant?
the EK D16y4 Engine doesnt have a bleed valve - I really prefer the set up on my EG - makes me consider adding one for the ease of it.