6.0 back fire
 

new to the page
I have a 2004 6.0 at the shop and the customers complaint is that after about 15 mins of drive time it starts bucking and back fires. been doing it for 4 years. We took it out on a test drive with our scan tool and it started acting up. Everything was showing normal.
icp pressure was good ipr good boost, fuel pressure, every thing was fine.
even when reving at about 2500 rpms at starts back firing

put a manual gauge on for fuel. never droped
has had all injectors replaced
icp ipr

thanks for the help
kinda stumped at the moment