I am thinking of putting a whole new exhaust system on my HX 1Tonner as the old one is beyond help and rego is coming up soon, so I need some advice about extractors and such, namely is it better to go with a dual system or is a single 2" system (which it has now) sufficient , taking into account that the engine and carby are pretty much standard, and I'm not a poser so I'm not after sound or looks they are of no consequence , I`m just after performance and fuel economy.