Scooterotica

Hi i have a ts 1 225 with a amal 34mm carb on when the engine is cold it runs very rough and needs to be revved up until it has warmed up then it runs perfect. when the weather was very
hot it ran fine from cold it also runs open with no filter. what is the best exhaust to use at the moment i have jl 3 i'm looking for low down power someone told me to use a fat mamba from pm thanks