Rear O2's Question
 

1)What's happening when I run the LS1 without rear O2's with an ECM which has not had the O2's removed from the program?
Am I running rich, or lean?
2)Under this circumstance, would the defining property be a total lack of control voltage from the O2's (an open), or would the ECM interpret this as the least amount of voltage which there can be (because of the open)?

The upstream O2s are used for fueling, the rear are for catalyst monitoring. If not plugged in at all likely to set rear 02 circuit codes (heater, etc). The ECM will know they're not plugged in, set codes and carry on.

The car does run but I'm wondering how the open ckts from the missing rear
O2's is interpreted...to what effect fuel delivery changes, if any.

It doesn't. The rear O2's are only there to make sure your cats are working correctly. Worst case scenario is they throw a code saying your cats aren't working, they have no effect on how much fuel is being put into the system.

ECM just sets codes with the info or lack of from the rear 02s. With them not plugged in at all it sees that circuits are not complete, and sets the appropriate codes. Will not affect fueling at all.

thanks!