It's that time again. Here's my story. I took the car in (stock 91 GT) for smog check it came back with high HCs. My mechanic takes a look at the car and says everything else is checking out fine, so the cats need to be replaced. So instead of having them just cut and place new cats I decide to just buy a new emmisions legal h-pipe. They switch out the pipes and I fill up with 91 octane and drive the car on the highway for 60 or so miles to break in the cats then retest. HCs are now in the clear but my NOx readings are failing; they have tripled to 900s. After some more research I find out these pipes are not CA legal; I specifically asked the guy over the phone if they were, he had said yes. At this point I just want my car to pass. Unfortunately i no longer have the stock h-pipe with 4 cats, as the shop threw it out. So my question is if I had the shop add carb certified pre-cats and cats to my new h-pipe would that be legal? Also anyone know of a smog testing center near Culver city in LA that would do a pretest before charging? Thanks in advance.