I had a Roush supercharger installed by Brenspeed performance. Costly, but a professional, turnkey install. My '10 STA 4.6L dyno'd at 525 hp, 428 to the wheels. It's a nice process, you hand them your keys on Monday and get the completed job on Thursday. If you are from out of town the will provide a nice place to stay while you wait.
brenspeed.com
Explorer & Sport Trac
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