1996 GMC Sierra Fuel Injection Problem

My truck is throwing an engine code relating to
a misfire every now and then.
The mechanic is saying that the popits on the injectors are in pretty rough shape.
I have run cleaner through the system over the years but this truck has seen a lot of heavy hauling and towing. It seem like I heard or read somewhere that there is an upgrade from the factory fuel injection system that addressed some of the issues with the factory original, although I don't really have any complaints with the original system considering the mileage. Do you know anything about an upgrade for this system? I am not really looking for higher perfomance, this truck seems to have plenty of power.