The 34 is EGR related. Was yours' KOEO, CM, or KOER?
Richness could be a bad/ruptured fuel pressure regulator diaphram, or a stuck open Canister Purge solenoid (goes to the charcoal canister). Check the vacuum hose to the MAP sensor too. If you've got a plug that ain't firing, it'll run rich. But you should be getting codes for the rich condition too. How fresh are the O2s? Are there any exhaust leaks near them?
Do you think the cats might be clogged? Back pressure will cause a 34.
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