Unless you signed a agreement with Novarossi at the time of purchase There isn't a fricken thing Novarossi can do about mods! Maybe they need to be a little more specific on there stupid threats I.E If I was to purchase a Novorossi take it home grind there name off and etch my name on it. There wouldn't be a damn thing they can do about it. Why? Bacause it's my property.So hey Novarossi I have six of your engines and I modified the $*it outa them I forgot what a stock novarossi sounds like!!! So I guess I'll wait to hear from your lawyers P.S. I love Novarossis engines but to me there a good baseline moter that needs to be wakend up!