Have run into a problem. Jeep has been running fine. Today when I left for work. On highway had loss of power (couldn't keep speed) and engine light started to flash. Oil changed this weekend & just filled up with gas. Runs OK till about 45 MPH then it's rough and hard to get more speed. Not sure where to look first. I am in process of pulling plugs to check. But I just replaced them, wires, cap & rotor only 12M ago.