As you probably know, the California Highway Patrol occasionally sets up their roadside dyno and does random roadside testing. That program comes and goes with funding, but it seems to be back on at the moment. So while I'd hesitate to run catless, the question is if they'd pickup on the long tubes when they look under the hood, which they always do. My guess is that they would. But, what's the probablity of you getting stopped in one? I think fairly low, but I also understand that it can get ugly if you do. Then again, if the car passes the sniffer with the long tubes and the cats, you may get sent on your way with no hassles, but it can be one of those things that always nags at you. I'd run a front plate and I'd try to keep the exhaust quiet, so you have less chance of being "chosen".
The check points are preceded by a large diamond shaped "survey crew" sign, But every one of the signs I've seen has been way too clean for any road survey crew. They also pick four lane roads so they can cone off the right lane for the testing and they have to have room for their equipment truck to park next to the testing dyno rollers.
I'd love to know the real hp and torque difference between the long and short tubes with high flow cats. I've always felt that headers kill some bottom end torque, but I've only ever owned what would now be termed as long tubes. I'm probably going to to the short tubes because I frequently wind up driving around in the 9 to 3:30 time periods the CHP seems to choose. The consensus is that the short tubes don't do much but I've yet to see a back to back test between them and the long tubes. My goal is the Magnuson, a better cam and the best heads I can get, combined with the short tubes and low restriction midpipes. I will probably wind up spending more and make less power than I would with non-A.R.B. compliant parts, but I don't want to be a pedestrian because they called a flatbed to confiscate the car.