i have a yamaha rx135.I want to change my exhaust system to a modified exhaust system ex: proton, or any other such. Exactly what are the issues which i should be considered about changing the exhaust and increase in performance as well as in mileage.Which is the best after market exhaust for my bike please advice and i am new to this place(Bhubaneswar) and i am unaware of any mechanic who is good with rx series in bhubaneswar kindly suggest me where can i find one of them so that my bike doesnot loose its appeal.