What exhaust did you install? Could you post a pic? Was the intake changed also? Louder exhaust usually means more airflow requiring more fuel. If all that intake plumbing was removed also for something like a RamAir foam filter or some other brand, you will be very lean. As already stated, Tune ECU will provide a tune for the earlier pre Roadster Rockets. Pick one that fits your model, then intake/exhaust profile and install. You will need a Lonelec cable also. Tune ECU is available as freeware for your laptop or you could purchase it for an Android device which is a lot faster.