Hello, I have a 94 mustang gt,it keeps dieing out,when i would accelerate,it would misfire and seem to lose power,i had a tune up done new wires and all that and i've changed out the battery,and i was also told it could be the fuel pump,how can one tell if its the fuel pump? before i go and buy one? also it wont read the diagnostic tester,keeps giving an error reading.puzzled,any suggestions?