Stupid me needs it spelled out: Once the AI tech level increases, it does not go back down even if AIP is reduced to pre-increase levels?
I think tech level will go back down, thankfully.
What does not get undone is the new bonus ships the AI gets after certain points in AIP (not sure what they are), so you get the AIP above some value, you see the AI start using a new ship types, even if you bring the AIP back down below that value, the AI will continue to spawn and use that new ship type.
EDIT: Ninja'd