There is a difference in how the fuel is injected between the two generations.
2007 injects fuel at the intake port/ manifold at 50-60 psi pressure.
2015 injects high pressure fuel (>2000 psi) directly into the combustion area.
I'll try running a few more injector cleaner and hope it frees up.

 

Also, some of these newer gen 5.3l can have several different injectors used per engine. They can have nominal flow, high flow, and low flow. The idea behind this is to keep the fuel rail pressure balanced and more even across the injectors for performance and efficiency according to GM. Be careful when taking the injectors out so that you don't mix up what one goes to each cylinder. Sometimes putting a high flow in the place of a nominal flow or low flow can cause misfire codes. GM claims that if something happens and you can't identify what injector goes where, a nominal flow injector should be used in it's place.

 

Also be sure to use a top tier gas, it contains a higher percentage of injector cleaner than the cheaper no-name brands.
www.toptiergas.com

 

3 years ago I went to a non top tier gas . I filled my truck and then put the 5 gallon gas container to use my lawn mower. well my truck had engine hesitations longer start ups.. so I put injector cleaner techron and added 3 OZ of MMO.. then the issue was fixed. my lawn mower had to pull the cord 5 times so I put MMO in the gas container and it ran better..
I use shell/exxon gas most all the time.
yes many had these injector issues on you truck. there was service bulletins on your truck .
I dumped GM after 2006 .. old GM is very good. new GM many had huge cost damages with GM poor quality on engineering and CCP parts made by slaves ..