[RobertM]

I was just going to ask if you had gotten any CELs since you added the 100 cell CAT. Looks like you've gotten one.

From the internet: Porsche error code P226D, meaning "Particulate Filter Deteriorated/Missing Substrate Bank 1," indicates a problem with your gasoline particulate filter (GPF) where the filter's internal structure is damaged or gone, allowing too much soot or particles to pass through the exhaust system.Symptoms can include a lit check engine light, visible soot from the tailpipe, and potential driveability issues. Diagnosis requires checking exhaust sensors and wiring, and the fix often involves replacing the filter

Because you added a 100 cell CAT the sensor thinks the internals are damaged and allowing too much soot to pass through. I would look for a 90 degree O2 sensor bung which will lessen the amount of pressure or air to reach the O2 sensor. This should trick the system into thinking the CAT is doing its job.

I know others have used 200 cell CATs without setting off the CEL. I guess that may be the threshold for not getting an error.