Kooks offers a "green cat" option which utilizes EPA certified cats, or so they claim. The majority of people that are using those cats are able to install without any codes without any tuning. They are NOT California legal though.
What problems are you referring to? I'd like to know so that if there are issues that I need to address or address with my employees, I can. It looks like we had a bit of back and forth by email back in March of last year about getting a tune, but nothing since then.