Synch the PC III to the T P first.
Think of it this way.
The basic map is in the ECU which the T P is connected to.
The PCIII is a piggy back device.
It does not hold a map, and instead holds a map adjustment.
So when your ECU is ready to send a pulse width signal to the fuel injectors, the PCIII makes a small adjustment to the pulse width signal.
The ECU map is a co-ordinate map based on a matrix of % Throttle Opening X RPM.
The PCIII adjustment is written into a matching co-ordinate map.
Now think of the two maps as two grids that have to be perfectly aligned with one another, just like two pieces of graph paper stacked so the lines are exactly matched.
When you synch the PCIII to the T P, it's just like the graph paper analogy I described above.
To give you an idea of what can happen if you don't, here is a real world example. Engine at 2 % throttle opening, RPM @ 1500. PCIII Closed Throttle Position error of + 3 %. What happens is that the PCIII will alter the ECU 2 % x 1500 RPM output with a 5 % x 1500 RPM based pulse width adjustment, and the fueling will be wrong for the actual engine condition.
My 919 was out 2 %.
My son's 600 GSXR was out 5 % !
You need to connect a computer to the PC3 to do the synching.
PC has a free tutorial on how to do it.
It is easy.
919s are super easy, patch your computer to the PC3, and simply turn your key on to "run". No need to use the 9 volt battery, no need to have the engine running.