Here are a couple threads. One dates back to June of 2001 that I responded on with the issue in question.
http://forums.mustangworks.com/showt...&threadid=2584
http://forums.mustangworks.com/showt...t=ProM+Bullitt
Seems like Pro-M may have fixed the problem, but there is a mix of people who had cold start issues, and some information about poor mapping in the midrange, etc.
I haven't heard about them offering a new calibration, so I don't recommend the Pro-M 75 with 24lb/hr injectors. Better safe than sorry I guess, hehe.