I replaced a head gasket and intake manifold.

I replaced a head gasket and intake manifold gasket my car ran perfect before I took it apart except it over heated. And I had oil in the coolant. I got it all back together and started it it ran perfect for about 30-45 seconds then it died abruptly now the only way it will start is if I hold the gas pedal to the floor and it runs extremly bad wont run at an idle and only goes to 3.5 rpm at the highest and I gotta feather the gas to get it to that I changed plugs and wires any ides on what is happening?