Driving in my 1994 Mustang Cobra Indy Pace Car, while in 2d gear when I hit 4000 rpm, it misses big time. Doesn't do this in any other gear. I don't know if it is fuel, or electrical, or something else. Sure would like to fix it..

engine will shut off while driving and will not start for at least 20 minutes. i have had alot of work done to it such as new lower engine, new starter, etc. Ford can not seem to solve the problem.