I have a 2000 mustang gt 4.6 with 95,000 miles on it. At idle sometimes its fine but every once in a while it will start lopeing between 500 and 1000 rpms. also when you accelerate if it is below 2500 rpms it seems to stumble like it is missing untill you get the rpms built up. Ihave new plugs , had coils checked replaced fuel filter, and there is no engine light on. seems like my gas mileage is not as good and problem seems to be getting worse. cant find any vaccume leaks replaced tps am thinking maybe Mass air, or EGR please help.