I just installed this exhaust on my 06. So far I really like it. The fit was perfect and this is definitely a well built high quality exhaust. My only problem is that its a little quiet. Im using it with stock y pipe and cats. I plan on changing the Y pipe but I dont think that will increase volume, only flow,Correct?

I was reading about test pipes. Living in Cali I realize these are illegal but I guess I could switch them back and forth every 2 years for smog. There are a lot of test pipes available,which one should I use so my engine light wont come on? Im new to these and I really have no idea...