Flexi 3450 air cart fan rpm

Hi there. Got a flexi coil 3450 tank, 2002, we use a case 9379. Hydraulics were always a issue, fan would drop when you lift the drill etc, so we said time for an atom jet. Got the atom jet and empty I'm pushing 4200/4400 rpm and the atom jet is full flow and it's a 28gpm pump. I should be able to max this cart out and set off high speed fan alarms. Anyone have any thoughts. The book in trouble shooting mentions about flow control at the cart. Best to our knowledge is there isn't such a thing. Also ours is VR. Frustrating cause we bought this and I still ain't getting the rpms I want. Can't remember how many rpm I gain it's loaded but I doubt it'll bring me up to 5000. Any thoughts . Thanks in advance

Flexi 3450 air cart fan rpm