Engine wont run right after it is warm

[CatDoctor]

I have a guys tow truck in my shop that when it runs for 30 min to an hour it starts to choke down he says, it won't run right. He has taken it to international cause it is in a tow truck and they cant seem to figure it out. They replaced a fuel regulator, he has replaced a few injectors with used ones, and he replaced the injector harness when he replaced a few of the injectors. I thought I would start hear cause I am stumped on this one. Any ideas?

[AMEC Electric]

CPS or IPR

[GRotman]

check oil level and quality. Monitor icp pressure and duty cycle, PW, fuel volume desired, and mass fuel desired. Compare these when it is running ok to when it is not. Should lead you down the right path.
Also try the ford oil aeration test....WOT for 3 min. this will tell you if you have any oil supply or oil quality problems.

[CatDoctor]

thanks fot the help but what is icp and cpc.

[CatDoctor]

I did some searching on these sensors, where can they be located on the engine?