I have an 04 f150 lariat. I have been told the some 04s have 05 engines and that there are a few differences between the two. Anyway, This winter my truck started to idle down (about (300-400 rpms) at redlights and such, then it would die. I had a miss back in the fall so I changed my sparks. Everything seemed fine. Oncwe the idling down started I was told to clean my IAC. I could not find it. Then I was told that my truck has an 05 engine and that they do not have one. So I was told to change my TPS. I did that and nothing. I was told to change my fuel filter, again no help. I have now decided to change my coils. Is this a good idea or what might be causing this. I am afraid it is going to die and cause a major accident. Worse, I carry my 1 year old daughter in this truck. HELP!

2004 F150 Lariat - 5.4 V8 - 101,000 miles.