My '86 GT quits at highway speeds.

First year 5.0 / 302 speed density(MAP) sensor fuel injection system, SIMPLE. The EECIV stores plenty of info and can be read in real time data will tell you everything If there's fuel pressure at the rail read PSI. Please POST the Ford dealers name so others can stay AWAY from them! I suggest scanning then based on the Info... Inspect the PCB 30 years matters. I have photo of a bad one posted on my "garage" click on my name and scroll to it.

Couldn't find it. Which picture?

Left to right (second row) 5th photo from the from the bottom.

The first Ford dealer that looked at the car and diagnosed a loose battery terminal, cost to fix $82.54, was Lance Cunninghamm Ford in Knoxville, Tn. Now I'm waiting 3 days for another Ford dealer, this time in Kingsport, Tn to even look at the car. I'm traveling from Knoxville back to Syracuse, NY where my RV is parked. Is there anyway a mechanic can duplicate the conditions where the engine stalls inside the shop? Where are you located and can you fix my Mustang?