So first I would like to clarify I know next to nothing about vehicles and engines. I understand 5.4ls are known for all sorts of different issues but in my case I have a 2004 ford f150 5.4l 3v with around 260k miles on it. During idle and driving it has a tick. It's not very loud but definitely noticable. It seems to be louder from the driver side. It's had that tick since I bought it but the last few thousand miles after say 30 minutes of driving that small tick turns into a much more aggressive loud ticking. It doesn't always do it. I notice if I baby the truck even on longer drives it sometimes does not turn into that aggressive ticking. I only notice the aggressive ticking after I stop driving, like stopping at a red light or so and strangely enough it will disappear for a short time. Say it's doing the aggressive ticking, I may rev the engine and it disappears but then a few minutes later it's back. The truck also seems to have less power during this time but it still able to drive and keep up with traffic. I can feel like it also slightly shaking the truck. I was hoping someone could let me know what's going on

 

I would say your entire cam phaser/timing chain/guides need to be replaced.