Are you still getting those codes? If so, then I doubt it is the transmission.

 

Nope not getting any codes anymore. I went to junk yard and grabbed six o2 sensors cleaned them with wire brush and all good there . Now i have spares

 

If the catalytic converter disintegrated, it could have thrown a bunch of junk back into the muffler and clogged it. Have you tried driving it with one of the down stream (just ahead of and just behind) O2 sensors out to see if opening up another exit point in the exhaust helps?

 

Will this cause a rich condition or lean?

Blazeme

 

An exhaust leak that is allowing outside air into the exhaust can cause a false lean reading at the O2 sensor which will create a overly rich condition in the cylinder since the PCM is trying to richen the mixture back up.

 

I got the leak at the "donut" fixed and also my tranny went on me so i got mine rebuilt.

And still the same problem

Things i have done:
new wires
new plugs
new fuel filter
new cat
changed oil
new transmission
new tps,maf,map
new egr modular
Did this https://blazerforum.com/forum/tech-articles-diy-29/96-fuel-system-diagnosis-23038/ everything ok there

still no mil light so no codes. I took it to a shop that did compression tests fuel pressure tests and they used a scan tool all they told me was "no clue im stumped"

Going back to the start ill take pics and logs

 

take a look inside your intake manifold, specifically at your fuel injectors. See if areas under or around some of the injector hoses are clean of carbon. You may have a leaking injector hose or two or three. They can cause too much fuel to leak into the exhaust and into the cat which can overheat and destroy your cat.