Custom OS and 2/3 Bar Tutorial.
"If your operating system is not listed (i.e 1999 and 2000 model years), you may use one of the 2001,2002 operating systems. Unfortunately, it is not possible to upgrade your calibrations to the new operating system. If you upgrade the PCM to a later year, you will need to retune your PCM for that Operating System."
Now, does this mean my existing tune(1999) can not be used as a base if I upgrade to the 2002 operating system?
What does it mean?
TIA