P1117 - O2 sensor heating after TWC - bank 1. Signal implausible.
This does suggest a problem with the sensor. The error is related to the heater circuit.
Some things you can do: Visually check sensor for corrosion.
Check sensor heating: Disconnect sensor connection and check resistance between pins 1 and 2. Read 9 to 10 ohms at 20C. Check sensor: Check resistance between pin 1 and the sensor housing. Check resistance between pin 1 and pin 3. Read infinite ohms.
P0140 - O2 sensor after TWC - Bank 1. Open circuit in signal wire or ground wire of sensor or the sensor heater is faulty.
P0136 - O2 sensor after TWC - Bank 1. Signal implausible. Short circuit to ground in signal wire. Intercore short circuit.
There are some diagnostics that involve checking the various circuits/wiring between the DME and the sensor connector and the sensor connector itself. I can make a copy of these tests in a PDF format and send it to you if you want.
Or, you can replace the sensor indicated by the error codes. I note all 3 error codes point to the same sensor. Thus I'd be inclined to the sensor indicated along with its counterpart on the other bank. I like to replace sensors in pairs to avoid introducing bank fueling differences due to the age differences of the sensors.
While I'm not a big fan of throwing parts at symptoms sometimes this is a quick way of highlighting where the problem might lie. (Another is swapping a suspected bad sensor with its twin from the other bank. This is a bit risky if one is not careful he can damage a perfectly good sensor in this swapping. This swapping then is intended to see if the behaviour/error codes follow the sensor or remain.)
I'm always reluctant to start messing with electrical circuits. In the case of the Porsche it requires some specialized break out box hardware, instructions for how to use this to test various circuits for your particular car, and in this particular case getting up close and personal with a volt/ohm meter with the DME which requires you gain access to the DME and disconnect it from the harness connector. If one is not very careful he can static discharge into the DME and ruin it. He can damage a connector, break a pin, or bend one.
By throwing new parts, O2 sensors in this case, and parts that one assumes work ok out of the box, if the symptoms persist then that is a sign one must delve further into some cause a bit removed from the sensor itself.
Now to the next pair of codes:
P1128 - Oxygen sensing adaptation, idle range, bank 1.
P1130 - Oxygen sensing adaptation, idle range, bank 2.
My references list "incorrect signal from MAF sensor" at the top of the list of possible fault causes.
Other possible fault causes: fuel pressure too high. Leaking fuel injector. EVAP canister purge valve open.
Since the error is present from both banks the fault this suggests the fault is a common one which points to: MAF, too high a fuel pressure, or EVAP canister purge valve open. While a leaking injector could account for this error on one bank the odds of leaking injectors on both banks are too long.
There is the shade tree mechanic's "test" of disconnecting the MAF at the wiring harness, and clearing the error codes and then just driving the car around to see if the MAF related error codes return.
There is some question in my mind about dealing with suspected O2 sensor problems and a suspected MAF problem simultaneously. I do not know how problems with the MAF might manifest themselves as collateral errors at the sensors. However a bad heating circuit and some of the other sensor related errors strongly point to a failure at the sensor (or with the circuit between the DME and the sensor) and not just something arising from sensor readings brought about by a failing MAF.