My car failed its first smog as well.
I got it to pass the second time by getting the catalytic converter nice and warmed up, drive for a half hour or so. I can second adding some pressure to the tires as well.
Pickup some Techron additive and run that through, either the tank before or during your test. I can't recall if mine had Techron during the test or not, but I remember it was either during or the tank previous. I found this quote online and it's attributed to Chevron
Techron Concentrate does lower emissions but may not lower enough to pass the test. If you use mostly Chevron gasoline you should be getting enough of the Techron in the gasoline such that you don't need to use the Techron Concentrate. If you have used some inferior gasoline and all of a sudden used Techron Concentrate, there might actually be a short period of time when deposits that may have formed in your fuel system are being loosened by the Techron and driveability may suffer a bit until all the deposits are cleaned out of the system.
Using Techron for a time before emissions test may lower hydrocarbon emissions because it cleans valves and combustion chamber deposits. We don't recommend going for smog test while Techron Concentrate is at its highest dosage in your tank. Run a regular tank full of gasoline thru first.
Before you go in for an emissions test, it is best to make sure the emission control system, especially the catalyst, is fully warmed up You should drive a few miles on a freeway or highway at cruising speed to ensure everything is warmed up before you take the car in for testing.
I've heard good things about this
additive, but I'd only use that as a last resort.
Good luck, and remember the most important thing is to warm up your cat converter.