3" exhaust is certainly worth it it will help with your response and will lower your egts slightly and sounds sick as well . As for the dyno if you are going there to improve they are the best way of netting gains out of your donk they have all the correct tools to make sure your air/fuel ratio is correct so you dont go doing any damage to the engine. If you get to a good tuner tell them what you want say 12 psi and i want it to tow reliably all day everyday for eg and they should be able to get it singing for you just the way you like