These are pretty simple circuits. Power is supplied to the injectors and the pcm toggles ground to allow fuel flow. Simply test for power to each injector. If there's no power, trace back to fuse and check for shorts. You have to check the injector resistance as well as that can cause a shirt if the injector has shorted windings.
There is a separate fuse for each injector in the under hood fuse box. There are 3 ECM fuses. One for the fuel pump and one for each fuel injector. Checking the wiring as Mr. 357 suggested is not a bad idea either.
My son worked on a buddy of his similar truck. It was running rough after replacing the transmission. They had looked at it for quite a while. I told him that I would fix it for $150/hour. His friend finally agreed. Took me 37 seconds and cost him about $2.50. The wires on the driver's side injector was not making connection.
Real, real easy diagnostic test is to swap the injector connectors.
Pretty common for them to get pinched and cut by the air cleaner.
And BTW, stop wasting money on parts, its annoying.
the injector on the left side is not working at all
Chevy Dealership or Repair Shop would be the cheapest route for you. You failed to actually mention what problem you are having
