Is there a way to check for bad 02's?

[gt93mustang]

... other than the check engine light. My car has started running VERY rich at idle, but has a miss and lean pop under load or partial acceleration. I was just wondering if I could check with a volt meter or if there was some other brilliant way to check them without just pulling them out and getting a new set. Thanks in advance.

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MAC equal length headers, MAC Off-Road H-Pipe, Flowmaster mufflers, 373's, March ram-air kit, underdrive pulleys, 73mm MAF, 75mm TB, Saleen Intake (ported), Edelbrock 6037 heads (ported, polished, 3 angle valve-job 255CFM @.500), 1.6 FMS RR's, Wolverine 1087 Cam, 24lb injectors, MSD 6AL, Subframe connectors, Griggs Adustable Lower Control Arms, Lakewood 50/50 shocks, SSM Upper Control Arms... and probably some more in there I forgot