When i did my engine swap i tested for this already and didnt find anything... When i do a cold start the RPMs seem normal but sort of flutter. Once the RPMs slow down the engine will start to struggle and itll stall if i don't feather the throttle, which means the choke gets kicked off and then i really have to baby it until its fully warmed up.
At first i thought it might be the fact that i don't have the stock air cleaner on (with the exhaust heat thing). But it still does this when the temp is around 70, so it must be a vacuum leak right?