2012 rzr 900 stalls after given fuel

So I have a 2012 900 that stalls almost every time after given fuel. When let off of the throttle it’ll bog down and either stall or come close to stalling. Has a built motor with ported and polished heads, hd buckets and everything redo. Any ideas on what it could be? I have a video of it but can’t get it to upload. Any suggestions would help. Thanks.