Almost done

Finally got everything I needed to reassemble my engine. Installed new cam, lifters, rebuilt the heads, few other things. Engine went together smoothly, but now one problem, car feels like it wants to die in gear and has a slight shudder in P, but when I get on it, high rpms, runs great, does this sound timing related?I cleanded out the carb real good to and reset the fuel mix Before I tore down the engine, it she ran smooth no problems.
Author: sgp7679