Perhaps a vacuum line? I know that’s a generic answer but my old 2.5 liter YJ had the EXACT same issue. I replaced the manifold gasket and after I got everything back together it idled like hell almost to the point of stalling and even stalled from time to time, also took long cranks to start. Ran great once moving/under load. A couple weeks after this issue started I went to shift into 4x4 and it didn’t work (YJs have the shift collar on the front axle shaft to lock the passenger side to the driver side via vacuum operated actuator). I found the main line coming off of the axle and traced it to the side of the engine block where it had been disconnected from another line going to the manifold. Fired the jeep up just to make sure 4x4 was working again and it roared to life after one crank, purred like a kitten at a steady 800rpms, which means that disconnect was also causing improper vacuum in my manifold causing rough idle/stalling. I must have pulled it apart while disconnecting everything from the manifold. Completely different engine setup, but it sounds like the exact same symptoms I had. Hope this helps.
