Injectors have 267,000 miles on them. I checked the temp of my headers while it was running thinking if I had some bad poor flowing injectors the temp should be lower on that cylinder... On the left side I saw temps about 195-200 degrees on the right side they were from 150-175 degrees. I didn't let it warm up all the way. Reason for checking is I've noticed a kinda random popping sound coming from the exhaust can't hear anything under the hood... This sound may have been there before but is more noticeable with long tubes maybe. If I let it warm up all the way does anyone know what the temp should be? They art stainless headers if that matters. Or am I even on the right track

 

Anything is possible with that amount of miles. Are the injectors stock and the truck is stock? It could be any number of things. A backfire out the exhaust could be caused by a misfiring cylinder dumping raw gas into the exhaust.

I had a similar issue on a V8 swapped S10 that had bad designed headers and they would burn through spark plug boots every ~500 miles and the spark would arc to the header. I would know the boot was burned through when the engine started backfiring out of the exhaust.

A basic tune up consisting of wires and plugs could be a big help. I'd try that first.

 

The engine has 40,000 miles I put a cam and tsp headers and tune on it. New spark plugs plug wires are kinda old tho. Yes the injectors are stock i reused my intake and injectors its not a loud pop you kinda have to listen for it and the truck seems to run fine...

Ht-1 cam 5.3 - YouTube

There is a video of it if you listen real close you can hear it hopefully that helps

 

To clarify I got a used 5.3 with 35,000 miles to replace my high mile one and did a cam swap on it before I installed it