backfire

I have a 92 mustang gt, the engine runs fine until is warm up and start to die on me and when I hit the gas it backfire, I took it to a few auto shop and they keep changing the sensors and it still does the same thingg what can I do?, I change the spark the plugs the idle sensor they toll me it cold be the thermostat and they change it. I am runing out of Ideas, I think it could be the fuel pump but the mechanic told me that it has good pressure.??? What will be a good solution to this problem.



V/r,
Javier

Check exhaust in ports 2,4,6,8 for proper backpressure