i have a stock exhaust, but i was actualy thinking to replace with 2brothers soon. I guess will need to change the exhaust if going there.
Another alternative in my area is sonoma raceway. Is it also same there too?
Correct. The Two Brothers will be too loud.
Sonoma does not have a sound limit, though running an open pipe may get you some comments in the paddock. The Two Brothers pipe will work just fine there.
Most tracks have a decibel limit, but Laguna is the only one I know that enforces it. You should be fine at Sears Point (just kidding, it's Sonoma now). Don't even bother going to Laguna with a Two Brothers pipe. You get one noise warning with a chance to fix it, then you are kicked off the track, no refund. It's the track, not the track day provider.
They have a three strike system. If you blow sound, they'll end your session immediately with a black flag, tell you about it and give you the chance to quiet your bike. That's one strike. Three strikes and you're out.
They also offer you the option to go out and do a sound test. When you roll up to the starter, let them know you'd like to do a test. You'll be allowed a few laps, and if you pop sound, they'll call you in, but without a penalty. You can also request the results of your test. As long as you request a test and show improvements, they'll be reasonable. If you go out for a second test and show no improvement or worse yet are louder, they'll start adding strikes.
This is all ultimately due to the racetrack being on a state park and neighbors complaining about the sound. Other tracks that are privately owned typically don't have sound restrictions.