OS160, Hatori header and muffler (not a tuned pipe, just a long muffler) and Cline or Iron Bay regulator. This is a no-nonsense set-up. It runs wonderfully on 10% nitro fuel. Place the regulator just behind the needle valve, NOT between the needle and carb.

This is as inexpensive as you can get and have all of the power and smooth running motor that will be as competative as any other 2-stroke combination. No, it is not as elegant as some other set-ups, but if you wish to have simple and plain efficiency, this will do it. The big advantage with the Hatori exhaust is that there is zero peakiness, not pipe length questions.