Rough Running 87 Grand Am

I have been trying to troubleshoot this rough running 87 Grand Am for too long now. It is running very rich and eventually fouls the spark plugs. When I bought it, the previous owner had replaced the injectors and the Ignition coil. I have replaced the plug wires, plugs, The MAF assembly, the O2 sensor, the Idle Speed sensor, cleaned the entirethrottle body assembly and installed new gaskets, and so on. It still runs rich and coughs and sputters and idles rough. When it dies, and I go to start it again, it seems to turn over one or two times and then it seems to "Bind". It seems to have some sort of restriction keeping it from turniong over smoothly. When this happens, I have to pump or hold the gas pedal to the floor for it to start at all. I am stumped! Any suggestions? Please?