2008 mp8 new conical injectors not seating with new injectors.

[57oldgoat]

Hi all, I'm new to posting here but here goes. I had 6 factory new Delfi injectors and aftermarket cups installed in my 2008 mack mp8 due to hard starting. Overhead was done and once engine was started, it had a hard time of maintaining fuel pressure. Filter housing was replaced as I currently have 906,000km on it. Fuel pump checked out ok. It was determined that there was fuel aeration occurring at the head. Pulled all injectors out and #2 and #4 were clearly leaking exhaust between injector and cup. I brought all injectors to where I bought them from and had them cleaned and inspected. He said that they all passed with better than new results. So I had them all reinstalled with new oem Mack injector cups. Went to start engine and it would barely start at all unless someone was constantly pumping the hand pump on filter housing. Again there is air returning into fuel tank. New injector hold down bolts were used both times and current Mack Volvo procedures were followed on torque sequence. I'm at a loss here on why are the new injectors and new injector cups not seating properly? I hope that someone has a solution as this is becoming a real thorn.