Hondata

I’m thinking about reflashing my 2006 TSX MT but i’d like to retain my stock ecu as backup. If i get a used ecu that has been reflashed can i send in my immobilizer and key to have it paired with the reflashed ecu? Also will this jeopardize the functionality of my original stock ecu?

I'm sorry, but this will not work. The key an immobilizer can only be paired to one ECU at a time. You should just get your original ECU reflashed and if you ever want to return to stock it can be sent back in. There is really no reason to ever return to stock.