S60 Detroit-code 61

I just replace a fuel pump on 1994 11.1 Detroit. Then I get 5 codes, all 61, "injector response timing too long." I learned that air pockets can cause this code and to just run the engine a little and air will be removed/flushed out. Didn't work. So I changed 2ndary filter thinking maybe not contaminants from pump helped clog, and not enough fuel pressure to flush air out. Didn't work. I talked to a gear head who runs a shop, but couldn't get me in until Monday, and he said it probably is the "orfice" at the return line fitting at the back of the head. I guess he was referring to the check valve. He also said that these should always be changed if changing fuel pumps. Does this sound right? Nowhere in my Detroit manuals does it say to do this. Moreover, does it seem possible that enough dirt particles less than 10 microns (2nd filter rating-I think) could prevent the valve from opening, even with 75 psi fuel pressure (Truck has a FASS system and that has always been the psi measured)? It's a real pain to reach that check valve because the truck is a Century. And I don't want to build a fuel pressure measuring system to attach to see if there is restriction. And I am trying to avoid driving to a shop for them to check because it's like it is running on one cylinder. Help, please!

 

Do you mean the 3/8 NPT male to female elbow fitting, that has-if I remember right-a what the Detroit manuals called a R-80 restriction?