I don't know if it holds true with the picco maxx engine or not, but the normal picco's take a lot of fuel before they are "broken in". Think in gallons, not tanks. So your going to have to fight with it a bit for quite a while, but once it's broken in, it should reward you with good power and a long life.
I have a picco p3 28 new in box that I never used in anything. May just keep it for nostalgia at this point since you can't really get parts for it. I know that one requires at least a gallon before it settles down. It was the "go to" engine for savage guys for many years, a decade ago.