Isx 2350

[Tcarpenter]

Looking for some help and guidance. Truck is a 2015 international lonestar that's been permanently fixed for well over 400k. Shop south of atlanta did the fix. With in the last 8k miles, the truck with fluctuate idling. Does matter if it's set on high idle or not. By insite truck is set to low idle at 700 rpm. It will start then when I first start the truck but by time it builds air it'll be at 900 for a few seconds then drop down to 800 and go back up. Even if I do highnidle it'll bounce around a couple hundred rpms.

I've done injector performance test which it passes. Looking at fuel pressure on data logger it'll command 10878 and the measured will bounce around from 10780 up to 10943. I'm kinda at a lost, I have no codes what so ever. Not real sure where to start at and not wanting to piss money away.