this happened in my old car and it sorted itself out so i think it is because the ecu has been out and it needs to get into shape again, but thought i'd ask.
rev engine, under load or not and revs drop to 400rpm, straight up to 900rpm, up and down 2 or 3 times then levels and is fine.
was fine before ecu out and battery disconnected. Will it learn and sort itself or from limited research i need to do a TB clean and TB allignment?
I do not think its the remap. AGU engine.