From what is inside the ECU for the 04-05 ZX10, they use 5 ignition maps.
1 map for all cylinders in neutral.
1 map for cyl 1 used in 1st through 6th gear
1 map for cyl 2 used in 1st through 6th gear
1 map for cyl 3 used in 1st through 6th gear
1 map for cyl 4 used in 1st through 6th gear
The TRE makes the ECU think it is in neutral all of the time, so it uses the neutral ignition map all of the time. The neutral map has more aggressive ignition timing in the lower RPM range, so it will help in that area.
Now the downside... Since it thinks it's in neutral all of the time, the neutral secondary throttle maps are used instead of the correct maps and the fuel compensation for ram air are not used, so the faster you go, the leaner the bike runs.
In case you were wondering, the 06 and newer ZX10s do not have a seperate neutral ignition map and only use the 4 individual cylinder maps in all gears, including neutral. There is no change in ignition timing when using a TRE on these bikes and you still have the same downsides as the 04-05 ZX10.
This is not anyone's opinion. This is what is in the ECU.
Let me know if you have any additional questions.
Thanks,
Don Guhl
Guhl Motors