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well actually i think that the piggyback SMT-6 works b/c it is in-line to the PCM ( so it intercepts the circut comming from the sensors) and then it inturprets them and then sends the signal to the PCM that will make the PCM say "oh crap it needs more fuel here and more air there" so some things like that do work..... but yea.... like MS works in a similar way i think....