Question on Boxster 02 Sensor

My 2000 Boxster S suffered from 1128 and 1130 codes for years. Replacing the Mass Air Flow sensor - twice - didn't seem to help I bought the Bosch version from Pelican. When we replaced the engine this year with a 2002, because of coolant in the oil not the heads or gasket, it came with its own O2 sensors. I thought my check engine light problem was solved. But... no luck... this engine runs great, smooth, better than the original - but codes 1128, 1130 1115 reappear within 60 or less miles! we swapped sensors from the original engine - no luck. We installed 2 new O2 sensors before CAT - no luck.
Please advise - how can I rid myself of this nemesis that has followed me to a whole different engine?!?
BTW... the computer is the original 2000 one - had to replace the wiring harness on the '02 engine to match it.
Thanks!

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This post was auto-generated based upon a question asked on our tech article page here: Porsche Boxster Oxygen Sensor Replacement - 986 / 987 (1997-08) - Pelican Parts Technical Article

[Nick at Pelican Parts]

With both banks setting the codes, look at something that can affect both. Vacuum leak, air oil separator, fuel delivery or the mass air flow sensor. Check when the fuel trim is faulty using a Porsche scan tool. Once you see when it is not in spec, you will have a better idea of what component can cause it. I can offer more advise with this data as well.

- Nick