I believe B12 is O2 safe. For the IC, the best thing to do is remove it and flush with gasoline and then blow it dry with compressed air.
As far as fuel pressure too high, it depends on how high it is, I'd say it should never be higher than about 47-48# with the vac line disconnected from the regulator with engine running at idle. Turning up the fp will cause the car to run richer at all rpms/load. The baseline should be around 43# with vac line off. If running too rich and the computer can't control fueling (ie BLMs lower than 108 with a scan tool) then the O2 sensor can get fouled prematurely...not to mention poor gas mileage and loos of horsepower.