Interesting post.

This is regarding my 996 so I don't know if it applies.
I did the cutoff mod for my car and had a switch installed on the dashboard.

At around 35000 km, in sport mode I could here a very annoying noise coming from the left muffler.
Like a piece of lose metal inside the pipe and and it would repeat faster as I press the accelerator
.
It would not be there in normal mode but back when I switched to PSE ON.

I realised it would go away as soon as I drove above a certain speed, like the back pressure in the pipe would finally put that piece of metal back in place or something like that.

But the problem would reoccur (only sometimes) whenever I would start the car again.

Don't know if it's related to your post Dillinget but I thought I'd share my experience since the PSE are similar in technilogy between the 996 and the 997.