NHTSA Complaint #11492177 — 2013 PORSCHE BOXSTER

There is an open recall on my Porsche boxster, the Porsche recall number for this is AMC0. The recall involves reprogramming the car to reduce emissions in sport+ mode. My car has an aftermarket tune on the ECU, and the porsche dealership has told me that the recall is not possible due to this modification. If I want to get the recall done, they want me to pay to replace the ECU/DME. I also consented to and was charged for labor hours for the dealership to research any way to not replace the ecu and do this recall, but they found no method to do so. Are they legally allowed to refuse a recall due to modifications to the car? Should the cost to replace the ECU be covered under the recall? I can't seem to find any information about this online, so thanks for any information regarding this