I drive a 2001 ford f150 2wd 5.4 and this is what happened. I flushed out my heater core and complete coolant system yesterday put it all back together and proceeded to go on a road trip when i started i realized the truck wasnt running right and was really really rough about a half mile out of town my service engine light started flashing so i whipped it right around and came home. I went up to oreilys and they put their machine on it and it pulled a code for a misfire in cylinder 4, tps, and o2 sensor. well i bought all new spark plugs and a tps and replaced them yesterday still have a service engine light for tps after i reset my computer. and when im driving at a steady rate my rpms will drop and come up rapidly (without the ac or heater on) and when i floor it from any gear it will not down shift it just bogs down and slowly picks up speed, also when i leave from a dead stop you can feel the truck hesitate when i give it gas it takes a little while to kick in and go

 

Have you checked your fuel pump?