Carb issue?
Here’s one lesson I’ve learned in 30 years of dyno testing.......
You know how to tell when the carb you have is a good match for the rest of your combo?
When you can bolt it on, make a few slight adjustments with the turn of a few screws...... and it just works.
If there are no issues with the motor itself....... the right carb “works”...... and the wrong one doesn’t.
I have seen that scenario play out countless times.