I have a 1999 ford expedition 4x4. i was driving yesterday and 2 hours into it at 70mph and between 2000 & 2100 rpms the car started to choke out it stopped when i increased the rpms. the check engine light did flash a few times and then shut off. it did this about 4 or 5 times in my 4 hour drive. air filter is new i replaced the fuel filter about 3500 miles ago along with the fuel pump. i blew a plug 3 weeks ago and fixed it. i thought it might be the throttle position sensor but am leaning toward the egr valve/sensor/solenoid. plesae help?