I agree on the supercharger. Roush makes one thats available at Ford SVT
dealers, and Edelbrock makes one also. The Edelbrock is a better design using updraft and longer runners. It puts out way more Hp and torque also. But on a 2006, you need the additional cooling upgrade kit ($150) to relocate the thermostat housing to prevent overheating. I have a 2005 thats getting one later this year. The Edelbrock fits under the stock hood. The Edelbrock even comes with a programmer , unlike the Roush.