Depending on how hard it is to do, you can pull the injectors and service them, or even replace them. On the 7.3 i had the o rings would get eaten out by the bio, so over time oil would literally work its way into the cylinders. So new o rings and it was a new truck. If the injector cups are dirty, you can full on soak them and get them clean again, so they atomize the spray well. I've heard of the sea foam trick, the version i heard was to drain the fuel filter/ water separator, and full completely with sea foam. Then you start up, let it idle long enough to fill the injectors, then shut it off. You come back the next day or so, fire it up, then go drive the piss out of it for an hour or so. Apparently it will blow all sorts of shit out the tailpipe, a consideration if you have anything at all for a muffler or cat. That's why pulling the injectors would be my go to, because I'm sure you have that kind of stuff. That way you could literally set up a pop tester (you can make them) and see what they are doing first hand as far as if they are in spec and are spraying well. I went so far as to shimming my injectors on the 7.3, which is considered the redneck rebuild on them. Worked like a charm.
Another thing that old beast really liked was a product called archoil. It was a molyendium oil additive, and it really really made her run better. It isn't exactly cheap, but it helped the injectors big time by lowering stiction. Something to buy you some time.