I plugged my crossover pipe with a 30mm expansion plug. It took me about 45 minutes, minus the trip to the auto parts store and the explanation to my father that I was, in fact, not going to blow my motor up.
Difference? My pipes are mostly wide open right now, which is to say stupidly loud, so I doubt plugging the crossover has any net effect - but I sure do like tinkering with my bike.
