1988 LX Mustang is considered a "Gross Polluter"!?

I just had my 88' Mustang smogged today and is now considered a gross polluter. The guy at the "smog only" station recommended a new exhaust system with all new cats (4 of them). How do I get out of this cheaply and what do I do next to make my Mustang "street strip " worthy by California law?