I just bough a 2013 EcoBoost 3.5L with 130k miles. I has a slight shudder when slowly accelerating. I took it in to the dealer and they diagnosed a faulty coil and recommended new coils and plugs ($1500). I bought OEM parts on Amazon for $250 and replaced them myself. It did not fix the issue. Since I have all new ignition parts I think it may be related to the transmission. I did the drain and fill of about 5 quarts but that didn't make any difference either. I noticed if you step on it the miss goes away. Anyone know what else I can try?