Hi mate yes it does sound like it is overfueling,this will cause heavy smoke under load,if it was not doing this before it blew then it must be something since,is the air intake as should be and clear?after that it is normally down to injectors and or pump,have the injectors been out when the head was done if so are they seated correctly?worth a look i have seen 2 seal washers fitted before and nozzle not in correct positon and affecting atomisation,due to cost time and effort i would get the injectors checked first.Hope this helps some Herald.