You did fine. The SCT Xcal2 MAP is $375. Once dealers install tunes, it can be a bit more depending on the complexity. The SCT 05/06 Mustang GT tunes are dead on and will make your car perform well. Enjoy the extra power.
me likey! still running the 87 tune for now...itching to fill and tune w/ 91
better throttle response, more power, more growl (most noticeable at 3k and up under heavy throttle) you feel it in the mid pipe, hear it from under the hood and the stock exhaust note is way more meaty
i do keep my tuner and stock intake on me all the time though just in case i need to go back to stock in the middle of nowhere but i've checked the hose clamps, MAF and other fitments a couple of times since install and everything is still tight as a drum.
this car was bad @$$ stock but now it's a different animal. this and 4:10's may be all i ever do.