First issue

First issue... when I bring the throttle up past 2500rpm and reduce it quickly the engine quits. It drops to 500rpm tries to recover for a moment then dies. If I do it slower it’s fine. Idle is a bit rough and if I push throttle in quickly it stumbles between 2200-2500 rpm, then recovers and keeps moving. I. Thinking mixture issue either air is leaking into manifold and making it lean, or mixture is set just a bit too lean.