07 ISX 871 heavy miss 1300 rpm +

[Sevalliere]

Hi everyone, new here seeking help. I have a truck with a heavy miss/skip at 1300 rpm +. Truck is fully “ de-mandated” by previous owner. Ran good for 8 months now has this problem. Hooked up to insite to test injectors and it says to start engine. Aparantly this tune removed nessesary programming to test injectors. New here and not wanting to piss anyone off but would be great if someone could point me in the right direction. I’m in Massachusetts and know of a few very reputable people to have look at it but they are overloaded with work already. Thanks in advance.