Re: AIR PUMP REMOVAL. what to do about AIR holes in headers?
No one has a later truck book that covers AIR?
Anyways, on the car systems (which are generally very similar/identical in some respects) AIR is injected into the manifolds ONLY when the engine is warming up. (open loop) Once the engine goes closed loop, AIR is diverted to the cat converter. If you have no pipe to the cat converter, then it likely diverts into the air cleaner once the engine goes closed loop.
Cars ran a pipe to the converter, but I don't recall my '83 K5 having the extra AIR pipe on the converter.
Look at the system and see if you have any electrical plugs to the AIR system under hood. If you do, unplug them. If no check engine lights come on, you are golden. Since AIR is injected into the manifolds closed loop only (again speaking from car point of view, truck manual should state how it operates) removing it has no effect on the O2 sensor.