rich f150

ok here's the problem, about a week ago I went to pass a car, stomped it pretty good and my engine revved funny and didn't accelerate much. let off some and it picked up fine. Now, I thought it needed some carbon blown out (I usually drive like an old man...lol) When I did this the engine light flashed about ten times and stopped., so I did it again and again, always the engine light would flash and stop. Then it came on solid and stayed on. Took it to the dealer and it said misfire on 4. Instead of taking a chance on breaking off the plug (poor design....another topic) they swapped the coil from 4 to another cylinder and told me to try again. The light flashed again so I took it back....this time it said multi cylinder misfire....mechanic said to run some seafoam through it and if that doesn't do it we may have to check the fuel filter and pump. My question is this, does it sound like the mechanic is on the right track or should I get another opinion? By the way, this is driving me crazy, I am kind of OCD about my truck! LOL thanks!