Yuza wrote:..maybe the oring in the slider guide? Ultrasonic cleaning might have moved it or damaged it...?
I hope you dropped the carbs in the ultrasonic cleaner disassembled

Ultranic cleaning leads to a lot of fine rubbish. When carbs are "cleaned" without disassembly, a lot of dirt will be "trapped" behind the fuel/air jets.
In that case, your air jets could be clogged.
Yuza wrote:I am now thinking of the main needle, might be worn!
A worn (jet) needle can be identified by just looking at it.