KTuner.com

I reflash my 04 Accord CL9 K24A3 with my new KTuner 04-06 TSX / Euro CL9 ECU
I use this map from KTuner program


But I have a problem ...
The car is much slower than with ОЕМ ECU.
Any idea what could be this problem? Bad map, ECU or something else ?

There are included basemaps to use as a starting point. If you want to get the most out of the vehicle you should tune it fully.

I thought that this is ktuner reflash map ...
Yet this basic map is much worse than my base ECU map obviously ...

It is the reflash map. A basemap is not one size fits all. If it's not running well for you then you may need to adjust and tune it. This is a tuning software to do just that with.