Hi guys, I am new to this site but a lifelong chevy driver. Heres my problem, I have a 2001 S10 ext cab 4x4 with 149,000 miles. In mid febuary I replaced the fuel pump, about 2-3 weeks later the truck starts what i would call chugging or surging when driving. It does not matter what speed I am driving when this occurs and it is spewing black smoke like a diesel. It may do this for days and then not do it for a day or two. I have also changed the fuel filter, plugs, cap and rotor and temp sensor but problem still exists. I have had it to the chevy dealer and they can't seem to find the problem either. It acts like its running out of fuel but all the black smoke would seem to indicate a rich condition but then it stalls when slowing down or at stops. HELP!!

 

Also I have changed the air filter and fuel filter. You can also smell like a sulfer order when truck is running rough but it has good exhaust pressure at end of pipe. I also have cleaned mass air flow sensor and EGR with no difference and replaced the O2 sensor on drivers side, one code that has come up is AIR bank 1 but not sure what that is. Could the pressure regulator
cause this? I'm pulling my hair out, HELP please.