I have a 2004 z400 it runs great intill I hook up air box hose to carb then when a gas it full throttle it Boggs and sputters no power I'm lost if I take it off and leave carb open runs like a champ. Has uni. Filter

 

Welcome to the forums.
I'd clean the carb.

 

Is your filter too sticky with oil? The spray can be put on too thick and actually restrict air. Enough air for idle gets through but not enough for full throttle. Easy fix but very frustrating to figure out. Hope it helps