My problem is it run great most of the time and then bad?

I am going to remove the rear pump and filters at the tank.

It seemed to die when I had to drop the rpm and speed on a little hill that has bad section at the crest as I started to throttle up it lost power.

then I had to feather the throttle to get another km where it could not climb a small 7% grade so I rolled it down hill into a recreation site and left it parked. When I get back it will probable run again.

Do the factory lift pumps or injectors ever get air leaks anywhere? (since the car had troubles a few times when I drove it around for 3 months (the body was rusted out and it only has 140,000miles on the drive train)

Do the injectors ever act up prior to needing a rebuild????