I'm researching this too. You'll find that people here highly recommend Paul Svincki at Paul's High Performance [paulshp.com (517)764-7661] and Gene at Performance Ford [performanceford.com (877)678-5591].
Both have received very strong praise for their product and customer service. I may consider one of these two, and they charge $340-$365 for custom chips which will program for premium fuel and increase the rev limiters.
Others on this site, and performance drivers at Ford Racing, suggest paying almost twice as much to have a chip custom burned while running on the dyno.
I learned all this here doing various searches. Good luck.
Due to cost reasons I will most likely end up going with option #1.
I am pleased with my Paul's chip so far. I think it may have helped increase my fuel mileage as well as throttle response. I know it hasn't for whatever reason,maybe traction,reduced my ET yet.But some things don't show up on the track.
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