Yes, sounds like you got it!
Did some digging and was just going to do a test and see if "Unused Byte 42" was it.

Thanks for posting back your results!

Jim

Following along - planning on adding a performance mode switch to my 9C1, but haven't wired it up yet.

Did a quick look and didn't see the performance mode state in eehack or Tunerpro RT, but it...