Tuning wild hp 450

[gvanminnen]

I have a quad the gasgas wild hp 450 2004

I want more power so I ask the dealer for some advice.
He say you can change the valves but you have to do it with the ECU.

You can't change only the ECU or only the valves he said.

For the valves I can take gasgas tuning valves of valves from a new type or yoshimura valves.

My question was:
Do you have to change both? (ECU and valves for more power)

Which valves are better?

Thanks.