Sports cat are one thing but de-cat, i cant see how you will get the EML off without a re-map, the ECU will throw a wobly until you program it otherwise. After i had a full through system with HFC's my EML came on after i booted it down the motorway, The codes (yes codeS plural, as this will throw many emission/02/co2 related codes) were all checked and found to be related to the cats etc. A remap is the only way unless your attempting to do something i'm not aware of to trick the ECU.