Cm 870 IFSM and CM 871 the same? Code 482 low fuel pressure

[Craag]

Can anyone tell me if the IFSM on the 2 motors is the same? Part # 4955685 for the cm 870 apparently not available according to my dealer. Tanks full of rubber crap and apparently they believe 100% it's all in the IFSM which either has to be removed and cleaned out or replaced with a part thet can't find anywhere. They said there should have been no restrictions above 3 in the IFSM and mine read 22! Any help or guidance is greatly appreciated.

Truck has been giving code 482 low fuel pressure. Loss of power, some hesitation and a surging idle early after start up that goes away after it's warmed up or re started.

Thanks!