IS3100Z with 37 hp Kawasaki cuts out and idles terrible when warmed up

I have a 2013 IS3100Z that ( when cold) fires right up idles fine and mows terrific. But after about 45 minutes of mowing it will occasionally lose power momentarily then catches and runs fine for abit till it does it again. If I stop and idle down will barely keep running or die. Let it sit for 15 minutes or so and it's good till it gets warmed up again. Changed plugs, fuel filter, fuel etc. Maybe a coil package ?? Thanks