Ever since purchasing my 2004 mustang over a year ago, it's always had one issue since the day I drove it home. After driving it for about 30 minutes, give or take, it just stops accelerating. The RPM's won't go up, it's as if the car is dead. I must note that It has never ran hot. You can floor the gas, and it just goes down until it stops completely. If I pull over and turn it off for 10 seconds, and turn it back on, it starts with no problem and will run fine again for 5-10 minutes, then the whole process repeats until I finally make it home. I should note that this car had a new engine put in with only about 135000 miles, and it is automatic. It's a V6 3.8L. My engine light comes on at times, but it doesn't always stay on. Although Sometimes when this problem happens, my engine light flashes. I should also note that the problem seems much worse if I have to go up hills, or make multiple stops at stop signs or red lights. When the problem happens, the car also sputters/stalls/jerks until I pull over, and if I leave it in park instead of restarting, the idle is very rough. It might also be worth mentioning that when parked, I can always notice a ticking noise, but I don't hear it when I drive and I'm not sure if that's related. Some other info maybe worth mentioning, is that we've never been able to get the car past 95MPH, and it will start running kinda roughly at about 80-85MPH, as if it's about to do that thing again. All the fluids/oil in my car have been kept up with. The code reader at auto-zone read for "O2 sensors." We replaced one and still have this issue. The fuel pump and fuel filter have been replaced, and the EGR sensor was replaced. I tried driving it with the gas cap loose, and off, thinking maybe it wasn't ventilated properly, but still had the issue. We put stuff in it to clean out my gas tank and try to unclog anything, and it does run a bit better but my problem remains. I am at such a loss, it's been nearly two years and I have no answers. Please help.