Wasn't the engine light or did they install some sort of spoof to fool the computer?

no engine light no codes

So something must have been done to fool the PCM then, yes.

yes my thoughts are to leave it out? wire is hiddin in harness no codes no light maybe removed because of headers im guessing truck ounds like a blower engine when warms up and idles

My 94 sets an 02 code after about 10 mins of driving and it still runs fine. I suspect you have another issue.

When emissions tests were still going on in Ontario one of the drivers at work couldnt get his truck to pass. I scanned it and it had an O2 code and the scanner showed the check engine light as illuminated. The light was not on so it must have burnt out. I replaced the sensor but the code came back. I sent him to a shop that I knew the guy that did the testing. I called and he said he would probably be able to make it pass. Apparently if you lie and input into the system that the truck ecm wont communicate you can do a tailpipe test as long as there isnt a check engine light. It passed the tailpipe test.

Does the check engine light illuminate at initial key-on?
If we were talking later OBD2 with a missing downstream O2, I wouldn't bother, but I kinda have to believe it'd run better and get better mileage with the single "upstream" sensor installed...

It will illuminate with initial key on. You'd certainly see better fuel economy with a working o2 sensor.

supposed to rain here tomorrow so truck is in shop im thinkin lets geter in there see what happens i do see the light when starting truck is harder than usual on gas

1993 is OBD1;
1995 was OBD1.5
1996 was OBD2
It is possible that the Corvette went to OBD2 earlier.

I believe that the O2 readings are not of huge importance back then.
I had disconnected the O2 on my 1991 Grand Am when I first did a header install (no bung) - it ran great off idle, it was only on idle that it ran rich.

Since that truck is OBD1, have you checked to see if you have a 'Jet Chips' or 'Super Chips' chip installed in the ECM?
If you do, that would lend an explanation as to why the lack of O2 isn't causing issues or an SES light.

1994 was OBD 1.5 as well. When diagnosing the knock sensor fault on my Buick I found out quite a few guys are programming custom PROM's for their OBD1 cars. You can buy blank PROMs and the hardware to write to them with you PC using software like TunerPro

just because theres a plugged bung on the drivers side doesnt mean theres not an o2 sensor on the pass side i learned that today so i pulled the plugs they had the white crust on them serviced them much much better will change o2 sensor when i get it on the lift no budge i check codes with hairpin every plug came out with a sparkplug socket and a wrench on the end of it due to the edelbrock headers,wasnt too bad