I would opt for custome tunning. You will get a much better setup for your car. Make sure you include anything you have put on the car from intake to tailpipe and your elevation. I use a tuning shop locally and have had outstanding results.
http://www.fastchip.com
They are located in Tulsa, Oklahoma. I have personally met a guy who brings his vette down from Denver every time he mods it or changes supercharger setups. When I am done modding my 05 I plan to take it to them.
I don't believe they work on fords, but I bet they can recommend somebody.
Good luck.
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05 GT Premium (all the bells and whistles) - soon to be retro eleanor/like to be twin turbo
05 2500HD 4x4 desiel - when I need to feel "manly"
04 CTS-V - wifes suburban race car
04 RC51/RVT1000 - to get away from it all
01 Z06 - to try to exceed 200mph
83 S10 prostreet 454 - to scare the H#!! out of myself
..."I want the truth!" "YOU CAN'T HANDLE THE TRUTH!!"...