I have the Yoshimura R77J on my GW250. With the stock air filter, there should be no problem and it should not require further tuning. Of course if you’re gonna install a K&N aur filter then there will be problems if the bike is not dyno tuned. The Yoshi is awesomely light (<3kg vs 18-19kg stock silencers) and sounds fantastic. I’m very pleased with it.