Not perfect RPM range...

baldy110 wrote: Really, yes you can get carbs to run perfect at all speeds and rpm ranges. Been tuning carbs for over 40 years and I seem to dial them in perfectly. You just need to know what throttle setting effects which carb circuit then tune each circuit till it's perfect. EFI is not the magic bullet.
If the engine surges under neutral throttle which sounds like your problem then it's lean on the needle. By neutral throttle I mean your not accelerating or slowing down but keeping the throttle steady.

Thank you, its only happens in high RPM, not 0-6k RPM, but that make sense when it comes to lean needle?
So the hootest thing I can test is to raise the needle one step?

Yes

Today when I started for driving to work I heard a new sound from the engine... «thinking...» I dident use sound protection today, so I was not sure if it was a new sound or not, but when I drive home I had, and the sound was there, so then I was sure it was new.

When breaked on the engine it also come some smell from the exhaust...

When I come home I checked the nuts on the exhaust and they was loose...

Tigheted all up and the sound disapear... and it looks like it removed the issue with high load and high RPM....

I need to fix the issue nuts get loose over time, but I’m happy that the issue was found

That will do it.