Ford F-150 (2004-2008) :: Swooshing / Lifter Noise RPM Specific

As everyone can probably tell, I migrated from the 6.0 Diesel section. A few weeks ago I bought myself a 2008 F250 with a 5.4. I do have several questions: It is a 2008 with 116,000 miles on the odometer

The guy I bought it from had replaced the engine in it. The tag on the engine indicates a build date of 4-21-06. It supposedly had 40,000 miles on it. He told me that the mechanic that installed it replaced the spark plugs and replaced one of the timing chain guides.

What model year would the engine be considered for replacement parts and trouble shooting?

I do hear, what I would describe from the old days as lifter noise. It is not a ticking, but more of a swooshing, RPM specific, that is slightly louder when the engine is cold vs. warm. RPM at idle is perfect at 640, fluctuating only about 5-10. It idles very smooth, hardly detectable.

I do not know what kind of oil was used in the truck, but the filter was after market. I changed it to 5W20 with a **** filter the day after I bought it.

The rear end is geared 3.73, and coming from a chipped diesel, this one seems sluggish. I realize this is a very heavy truck for the engine, but should it feel heavy. The "lie o meter" tells me my MPG is 9.4 driving in the city. Have not yet had a good chance to take it on the highway.

So, to summarize in trying to learn the 5.4. What would the model year be considered. What should I check with the swooshing/lifter noise.