Are the O2 sensors working, what is the catalytic converter like condition wise etc? See if there are any error codes lurking in the ECU and correct any detected faults. There are all sorts of things that can affect a smog test. Even dirty or contaminated engine oil can be enough to barely cause it to fail. Use the lowest octane fuel you can get (85) and don't use any fuel additives (seafoam will clean out the upper combustion, but the solvent residue will insta-fail it), oil flush the engine to scour as much old oil sediment out of the block and sump. Don't disconnect the battery for at least a week before taking it in for an inspection or the ECU will be re-learning base tune and it'll throw it out of emissions specifications. Even have a crack at cleaning your injectors out so the spray pattern is uniform.