Well, l just wanna buy a wider air flow exhaust tip for my 250ex l am not buying the muffler l am not buy the entire system just the exhaust tip...Do l have to rejet?

tip is nothing but looks and no dont have to rejet for looks

Your exhaust system is precise to your motor is back flow..(exhaust) changing the tip will only change the back flow if you put one on that will ''restrict'' the release of exhaust.doing that may cause vapor lock or backfiring..and could cause the check engine lite to come on.since you are going bigger on the tip only..it will not matter.