Agree with CW...without the 02 sensor you can't even begin to do a proper diagnosis of the fuel injection system. The computer is always going to go into a "limp-home" mode without the sensors input.

So while there maybe another problem; the lack of 02 sensor is componding the issue.

The removal of the air injection tubes from the exhaust manifold (i.e. installing headers) will not cause any driveablitiy problems.

 

Without the O2 sensor the engine will run rich because the engine is running in limp home mode as was already stated. It should run OK in this mode without cutting out. I would plan on welding in that bung and getting an O2 sensor back in there. For now I would check the injector spray pattern to see how the fuel cones look.

Engine running. Look down in the throat of the throttle body to check the injector cones. There should be a fine cone of fuel with no gaps and no streams at the base of each injector. The cones should reach the sides of the TB. Low ambient light and a flashlight shows the cones best.

 

Limp mode - its safe. I believe in a correctly operating system your truck actually acts as if it is in limp mode for a few miles until the sensor heats up. You will waste gas, but driveability should be the same. My truck ran better with the bad sensor unplugged than with it plugged in.

My truck's issue was stalling, caused by crossed wires. I did note improved mileage with the new sensor, but that is all.

 

Good news! Drilled a bunghole and welded a bung to the head of my glasspack, then extended my o2 harness. Installed a new ngk and she runs like a dream, a very very loud dream. Thank you all for tbe help and advice!

 

I have been running without the air tube or pump. I tapped the exhaust manifolds with expansion plugs and changed to a cat w/o the air tube. However, I kept the EGR and O2 sensor. No driveability issues in over a year. If you played with the idle speed, like I did, be sure that you follow the proper procedure in the FSM. Mine would cut out and die once it got warm on a long drive and then progressively got worse until I correctly set the idle.