Air/Fuel adjustment question

[Pštros]

I have a 2013 Puma Valentine 150cc (the 1966 Vespa clone). I was into a new carb from the dealer within 50 miles for a malfunctioning choke. New carb made a huge improvement but still some acceleration issues. I watched about a dozen You Tube videos and tried adjusting the fuel/air screw.

After warming up for 10 minutes I find the bike runs fine with the screw ALL THE WAY IN. I don't suspect that's how it's supposed to work. No change to the acceleration after several 1/8 to 1/4 difference settings. Maybe a leak?

This is important because my wife also got a new BMS 150cc. We replaced the carb, before 50 miles, and it runs very smoothly and has great power. Why is mine a pig?

Thanks from a new member and first time poster!