2001 Saturn SL2 Engine idles low and stalls pulling away fr

2001 Saturn SL2 4 cyl

I'm having a problem with my 2001 saturn sl2. I replaced the engine a while back, and ever since it has been having a little trouble. It used to be that the car would rev very high when put in neutral and when apply the brake. Now the car runs pretty well, jumps on occasion while running, but the real problem is that it will stall when trying to pull away from a stop, or have difficulty starting and then die when trying to pull away. I had a diagnostic done which told me to replace the ignition control module, coils, wires and spark plugs. I did all that and nothing changed. I even cleaned the air intake and throttle since I heard that could be the problem. I'm stumped and can't afford another diagnostic that turns out to be useless.