2000 k2500 backfire though the exhaust

[Puke160]

My 2000 k2500 with the 5.7 and 4l80E backfire though the exhaust at all idle..
About 3000 mile ago i gave it a full tune up new cap and rotor, coil, plugs, wires, air filter, and cleaned the throttle body. And the truck ran great after that.

Around 400 miles ago i got what i thought was a bad tank of fuel. 10 miles after i filled up it started backfiring. I tried to just run though it, but 2 day ago my fuel pump went out so i drained the whole tank and started with all fresh fuel.

When i got it all put together it is still backfiring like crazy. I have a good stong spark on all my plugs. I really dont want to just randomly start replacing stuff but i am lost.

[Puke160]

I just changed the timing chain. And the old one was about an 1/4"longer and a littebit loose but not real bad. But it still backfires the same.

I also checked the valve train. Set the rocker and all the valves have full range of motion and none of them were sticking or binding.

So i guess im down to replacing sensors. Or the fuel injectors. Has anyone had issues with the injectors sticking open? That would explain the backfire in the exaust, the lost of power and the 6 miles to the gallon.

[Kudzupatch]

Have you checked for error codes?

Injectors are more likely to clog and cause it to run lean, not rich.

I would run a compression check before I started randomly replacing sensors. Replacement parts these days are just as liable to be bad as good. You could make it harder to find that problem. I am betting this is a mechanical issue, not electronic.

[Puke160]

The truck does not have any codes.

And I have not done a compression test yet my gauge got dropped and stop work.