2005 GMC Sierra ECM - PTCM

2005 GMC 2500HD Duramax. Have had injectors replaced and a new PTCM installed less than 5000 miles ago. Started heavy smoke. From the day the PTCM was installed mileage dropped 2-3 mpg. It started smoking heavy so took it in. All injectors were fouled as well as EGR, & turbo boost sensor, they cleaned and seems to run OK. Thing is that, I am sure that did not fix the problem. The injectors did not have 1000 miles on them when the PTCM was replaced. They do not want to replace the PTCM again. They say the injectors looked like they had 250000 miles on them, truck only has 66000. They have reflashed the ECM. Can I get a new PTCM & get it properly programed? I am told by several GM techs the PTCM can not be checked for proper function. I do feel the PTCM is the problem, it was junk when they put it in. My reasoning. 3 power steering pumps to get a good one, 19 injectors to get 8 that seem to balance OK. Their reman stuff is very low quality. Any info/advice would be appreciated