Okay,

Here is the situation. I finished swapping a B18B (from 01 Integra) into a 94 del sol using an OBD1 ECU. Got no CEL. But engine hesitates a little and is blowing out black smoke. The exhaust flange (after headers) doesn't line up the the car's exhaust pipe (just before the CAT). Hence, my exhaust pipe is open. There is an O2 sensor about a inch or so upstream from the flange. Could the open exhaust pipe cause the O2 sensor to tell the computer to run rich? It's blowing out a ton of black smoke. I have checked all of my vacuum hoses and they are all connected. Any ideas?