Engine problems

so I'm stuck on this one. Before I start I will list everything that's new (and not bad) because I know new parts can be bad, but this is just confusing. new coil, plugs, wires, distributer, and its correct timing and new fuel pump and I'm getting good fuel pressure. This morning, I had started to make sure I was getting spark and fuel, and I did not put in the new o2 sensors, just let it run to make sure I was having a misfire because I was before (I'm not now). As it was running I put the o2 sensors in (not plugging them in) and it killed the car, then ran fine when I took them out and turned it over. all new exhaust from long tubes to tail pipes.

rundown:
>car is running great
>screws in both o2 sensors
>car dies and wont start
>takes sensors back out
>car starts and runs good again.
 
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