Update time.
The lack of power problem was the fuel pump. 10yo bike, it was time already.
Replaced with a new one. Genuine, but not bought in Suzuki.
If someone be interested, this is the stock pump: Mitsubishi UC-T30. Many cars and other bikes uses this same pump.
Today I did a bit more for the SF transformation:
What I did this past week:
1. Fuel pump replacement.
2. Fuel filter cleaning.
3. Coolant reservoir replaced by an aluminum water bottle.
4. Stainless steel jack-up kit installed (5 mm shorter than stock).
5. Steering damper guard (alluminum).
6. Mirrors replaced (I broke the previous one during parkink).
7. Air filter changed for a new one.
8. Air box fully disassembled and washed.
9. Handmade ignition bracket (alluminum).
I'm now working on finishments to close the "wholes"
See ya.