Welcome to JUST ANSWER heavy equipment. With years of experience, I look forward to doing my best to help.
The indication is that it is starving for fuel. The fuel transfer pump is mounted right on the side of the injection pump. Item # XXXXX if you can make up a test line from the inlet on the transfer pump to drop back into the top of the fuel tank, This will eliminate the fuel suction system and see if that is your problem. If it is, then we need to look at each hose, filter, and clamps all the way back to and including the tank. You could have something in the tank suction tube keeping the fuel restricted. Let me know. Thank you.