I think the problems you are describing first need a general mechanic to get
the vehicle up to speed. Fine tuning the emissions system if the vehicle
doesn't pass the first test after the general mechanic is done with it, can
be diagnosed by a smog check repair center. The labor rate at a general
repair shop is going to cost much less (though you should confirm this with
the shop) then a certified smog check repair station. Just note that no
money spent at a general repair center can be used towards your deductible
if you decide to apply to the State Repair Assistance Program CAP.
White smoke may indicate a defective head gasket. White smoke is basically
steam, and is caused by water seepage into the combustion chambers. Water
may be entering the combustion chambers through the head gasket where the
engine's valve head and engine block connect. This will cause white smoke
coming out of your car's exhaust tailpipe.
Just note that excessive white smoke is normally emitted typically on cold
days, and when the engine is not properly warmed up. White smoke during
startup or during cold weather is just steam, and will not cause a smog test
failure.
