[87 GT MUSTANG]

Need help with this one. my car is a 1995 mustang gt and when i drive it for about 15 - 20 minutes the car just cuts out on me, there is still power but no throttle, the car just dies. I will pull over to the side of the road and try and start it back up and it turns over but it is like it is not getting a spark. I have replaced my plugs,wires,cap and rotor, and my coil is now 4 months old. I brought the car into ford today and they did a series of tests and they couldn't find anything, they checked the fuel pressure and that was fine, they checked my connections and those were also fine and they also did a test on the coil which also came back fine, they tried pulling some codes but there was nothing. Ford had also takin it out for a spin and the same thing happened to them, they told me there is nothing i can do unless i let them spend more time with the vehicle, what i would like to do b4 i let them do that is ask you guys for your help on what you might think it is.