failed smog test...hydrocarbons

When I had to pass the emissions here, I would use a 'Diesel fuel modifier' in a gas engine. I used the Amsoil product only around test time. In fact I would plan on a tank of gas to be run through the engine before testing. I am not selling the product, just letting you know what worked for me. The first time I used it was after I failed the test, and two days later it passed just fine.

...I used to put some octane booster in with premium, and ran it hard down some highway straights. Then took it to inspection hot, and left idling. The hotter the cat, the fewer hydrocarbons, and the residue and soot in the tailpipe has been blown out as well. Make sure the battery cables on both ends are good and clean also.

Battery cables for emissions?

...yes to make sure the ignition system as well as the electrical circuits are at their highest efficiency for proper burn.

Considering your battery does nothing but charge while the car is running, I fail to see how it helps

A less than clean ground can cause less than great firing and sensor inputs