Driven engine block off plates will stop the annoying and possibly damaging backfires from occurring while allowing you to remove a few pounds in associated valves and hoses from your bike. On late model EFI bikes with 02 sensors, ESPECIALLY when using Dynojet's Power Commander V with the Autotune feature, the air injection system MUST be blocked as it will introduce additional oxygen into the system which will skew your 02 sensor's values and make it impossible to get a correct tune.