Toyota: 91 Previa CA vs. 49 State difference?

Hi,
I bought a 91 Previa a month ago. It had Oregon tags & reg (150k mi. on
it). The seller made me a good deal, so we took it to a smog station here
in Ca, where the mechanic made a slight adj. (I'm guessing to the fuel
injection) and it passed smog. It's CA registered now.
About 100 miles later the check engine light is on, and the diagnostic
flasher tells me problems with : Oxygen sensor, sub-ox sensor & throttle
pos. sensor.
Did these all come about from the mechanic's tweak?
Will the problem return after I replace these parts?
And further, was I a bonehead not to think of this before buying?
Feel free to heap your ridicule on me as long as it's accompanied by honest
answers/opinions to my questions please.
Thanks,
Richard

"MDT Tech®" <com> wrote in message
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Thanks again! I'll check this group out also. Take care.