2000I30t O2- PO135 + CAT EFFICIENCY LOW- PO430 what to do

[Emile]

Want to drive car forever, but starting to get that feeling of diminishing returns when I get repairedhave over $2000 in repairs already invested

Here is recent problemservice light onlast week mech got PO135

came in this week to replace sensor[service soon light still on]

mech checked code again to be sure he gets correct partthis time both codes come uphe tells me come back day or so he will check againat this time service light is not on

I ask what to do because-129,000mi inspection good till 5/2009 NJdo not want a highway breakdownWant to keep car "on the cheap"

Any suggetions, even if I buy another car I would like to keep this 1, emotional connection I guess, yea, I am a bit crazy