Sorry for the delay in answering, and you may have already resolved your questions but here is my take on it.

If your Boxster has 4 Cats, 2 per side, one in the header and one near the muffler then you can do the 2nd cats delete (one near the muffler)) from Top Speed, and then you'll also want the Top Speed Muffler.

Without the 2nd cat delete you will get an intolerable drone around 3000 rpm, so don't do the muffler alone.

With that configuration I pass the CA smog tests, there is no dash light and the car sounds incredible without being too loud, but when you put the hammer down it Roars! yet still quiet for your average gentle driving.

You will love under bridges when the sound just echos right back at you with its aggressive sounding roar.

If you don't have the 4 cat system then you will have to come up with another option to avoid the drone of the Top Speed type muffler.

Hello I'm Josh. I have a 2000 Boxster S. I been reading what you posted about the top speed muffler and the 2nd cat deletes. I hope you can help me. My Boxster is my daily driver and all I want it for it to be a little louder. Not obnoxiously loud I just want it to sound like a Porsche. Can you suggest a way to make it Lou's but not to loud, have no drone, and able to not have the check engine light on please. I'm going crazy lol I hope to hear back from you soon. Thank you.