Hey mate, cossie is lookin good!
I can see what you have done to the engine. First up sensors are not going to cause the engine to smoke. It seems pretty simple to me, if it is only white smoke/steam comming from the exhaust. The problem is water, has the car used any water in the cooling system since you have done the work on the engine? If it is not using water from the cooling system then the headgasket has sealed properly. So the only other way steam comes from the exhaust is if there is alot of water in the exhaust, rain or alot of sitting around idling. So take the car for a decent drive at least half an hour get it up to temp and give a good boost, the steam should stop after this time. If it continues to steam/smoke from the exaust water from the cooling system is getting into the combustion side of the engine and comming out the exhaust meaning a failed headgasket.
kev