I congradulate you on those times. Keep in mind, my time is with 173k original miles on a convertible. You speak from experience with your previous foxes, and I speak from knoweledge read of many many mags, and racing many cars.
http://home.earthlink.net/~jfgalbraith/qtimes.html
http://www.mustangregistry.org/lx_85_86.htm
http://www.mustangregistry.org/lx_87_89.htm
Those are just a few sites, go ahead and read up. Like I said b4, the LX will do a mid to High 14, but for the other 90% produced, meaning everything with an automatic and everything non-lx did low to high 15's. Tell the professionals at road & track, at car & driver, at 5.0 mustang that they don't know how to drive.