If the plenum gasket failed could that explain no power at all and not being able to get over 1000 RPM. As I understand it a bad plenum could cause the cat to become plugged. I do see a lot of smoke come out tail pipe, could cat still be plugged even though I see exhaust?

Also does any one think it could be a bad fuel pump. I do get 48-50 psi at the rail but hard to gauge under load cause it craps out anything over 1000 RPM?

I had it idle tonight and the check engine light flashed a couple times again but didn't show any fault codes.

One more question, could my engine be in limp mode? Sorry for all the "can it be questions"

Sounds a lot like a plugged up cat to me.

Put a pipe wrench on the O2 sensor, and whack it with a hammer a couple times to get it to break loose. Shouldn't break the O2 sensor. See if it runs any better with the sensor out.

That's a great idea about pipe wrench, will try that when I get off work. I really cranked on the O2 sensor last night and it slipped or spread open, so I stopped before I rounded the o2 sensor.
I did remove the air cleaner and opened the butterfly and shined a light down there. I could definitely see oily residue which points to plenum failure. I ordered the Huges plenum kit last night. Been watching a lot of utube videos on replacing it. Been putting it off for a while now. But its time.
Thanks everyone for all your suggestions

Do you have emissions testing in your area?

Nope :) I thought about just eliminating the cat altogether.

Or I might try and gut the cat while it is on my truck, will it be much louder by doing this, or would it be better to eliminate it altogether?
Either way I am definitely going to put a pipe wrench on that O2 sensor tonight and hopey see an improvement.

It's a little bit louder...... A high flow cat is definitely an improvement over the stock piece. Big restriction right where the two pipes go into the cat.

I tried the pipe wrench and thought I had a good grip and it slipped off a little. Looked and it slipped on the o2 sensor and crushed it a little. I figured if I let it idle for about 5 min it would heat it up, then might be able to get it off easier.

I started the truck and it wanted to die so I had to constantly give it gas to keep it going. Right before trying to start the engine I banged on the converter a few times, thinking it might jar something loose. I was able to rev engine to around 1500 RPM which is an improvement.

Then the truck died and wouldn't restart, it wouldn't even fire at all, acts like its out of gas, I checked pressure at fuel rail while cranking and it still shows 50 PSI. Could it be a bad fuel pump or a bad coil. I'm just guessing now.

Or maybe the new crank position sensor is bad. Could a bad plenum gasket prevent it from firing?

If you have 50PSI fuel pressure, the pump is fine. Are you getting spark? Bear in mind, these trucks don't much care for aftermarket sensors in critical locations......