So my ranger seems to run well most of the time..My CEL came on and i pulled the code and it was for the EVAP system and a misfire in cylinder 1. I found that the purge valve was stuck open so I replaced it hoping this would solve both problems. It did until a week later I was driving home from work on a hot day and my CEL started flashing and then stopped after getting on the freeway. So i cruised home and pulled the code. Misfire Cylinder 1. Replaced the plugs. No fix. I didn't realize it at first but it will severely misfire always cylinder 1 after high rpms and then get off the throttle. Thinking maybe a clogged injector I put Seafoam in the tank. I ran one can and I seemed to fix it a little bit, so i ran another, but now it seems to be the same as before..Is it time to replace the injector or a totally different problem?

 

Make a home made stephoscope out of piece of old water hose,,, hold it to your ear and listen to a couple of the injectors while truck is running and see if #1 sounds any different,,, sometimes they will make a racket

 

If theres a mechanical problem on number 1 it should show up on a vacuum gauge or compression test

 

Welcome to FTE.
Post All trouble code Numbers you have, as they can often provide good trouble shooting clues.
All that said, the cyl 1 misfire after high rpm could be a number of things. Seeing as how it seems to have gotten better for a while after having used a detergent, then returning after some higher rpm highway driving, sorta makes me want to suggest a CCDF = Combustion Chamber Deposit Flaking problem. This condition is known to cause the kind of problem you've reported.
You might consider Techron Concentrate Plus, which is blended to specifically get after engine deposits. It'll also tidy up the fuel injectors, intake valves, along with the combustion chambers, Without leaving any deposits.
Use it at the specified treat rate of 1.0 oz/gal, at the pump before filling, so to get good mixing. If we fill up with Chevron, Texaco, Caltex, or now Shell, all of which already have some PEA in their fuel ad pack, the additional Techron will raise the treat rate 10X above pump gas alone & will often yield results in one tank.
Run most of the treated tank out, with some spirited daily driving, with rpm at 3600 for a mile or two, so to help remove loosened deposits & let us know how it goes.

EDIT: You said you replaced the spark plugs, so how did the #1 plug look on it's deposit read, compared to the others?