Any pipe besides Pro Circuit, DG, and FMF. Get a Toomey, Power Pros, or Shearer. It also depends on where you want this power too... From experience, the Toomey offers a nice Mid-top end power. I've HEARD that the Shearer was a Low-mid end pipe. I'm not so sure about the Power Pro's....Also you could spend $200-$400 on a nice port job, but in order to really feel the power from a P&P you need a new pipe.... Hope this helps....