Engine is smoking

I just changed the water pump, camshaft sensor, timing belt, serpentine belt and thermostat. Everything is back together and running great and at correct temperature. The problem I'm having is there is smoke coming from the front of the block that seems to be from somewhere under that hard line that the diagram refers to as the heated oxygen sensor. I had to remove that line in order to take off the intake manifold because it ran all the way to just behind it. I cannot see any obvious reasons that this would be smoking, and it has been long enough that any type of fluid that may have dripped has burnt off. Please help, it's the last riddle to solve before I'm back driving again.