Which gas to run?

Tons of people do what you are doing, I was one of them. I now have a chip in mine so I have to run 93, but if I had it to do over again I would stick with plus at the most.
Also Ford has a "theory" behind all of the rough start problems that have been bothering a lot of '02 and '03 GT's. They think that for some reason the engines cant handle the extra octane. Also they feel that it is causing excess evaporation in the lines thus causing the crappy starts a lot of us have at first start after the car has sit for a while. I think its a bogus theory.
Look at it this way though. A car runs 89 for many years, it starts spark knocking so you add in plus. It cures it and for a few years your fine, then it starts knocking again, so you move to 93 and it cures it. Now that your at 93 where do you go from here? Rough cycle huh .
Oh well, thats my .02c

With the stock timing and compression you are only wasting your money by going with the 93. When I had my GT I used 87 with no problems. This is what Ford recommends anyway.

I would say it is a personal preferrance thing. I run mostly 87 but once in a while I run 91. The higher octane fuels also have more detergent in them for cleaning engine vitals, so I am told. I figure if it is just a few cents a gallon, once a month, then it isn't hurtin me too bad, lol.

Bo