My 2010 GMC Terrain while maintaining a speed of around 60 - 70 mph starts to hesitate and if I don't release my foot from the pedal I will get flashing check egine. I've noticed it likes to happen more when the pedal is at about 50%. I have changed a couple parts out now, but the misfiring is only coming from cylinder head number #3. I've checked for any noticeable vacuum leaks, and nothing. I've now bought a obdII link mk+ I have readings, but nothing to compare them with. If you have any ideas, I'm willing to check it out.