Needing someone to maybe pinpoint problem with 99 ford f150 lariat

So lately I have started having what I think are lack of
motor power in my 1999 f150 lariat. When ever I drive it. It
feels like it's not getting the normal power and flow from
the engine as it use to. When I put it in park or neutral it will
idle and run just fine. But when I am in drive it starts
running a bit rough. If I'm sitting still in drive it will kinda run
but rough like its sputtering and almost wanting to sputter
out kinda but it will not die. It just will be idling then sound a
little groggy then back to rumbling and running regular the
groggy and crumbly. Also when in drive and actually giving
it gas it seems to have a little trouble increasing in speed
and not staying constant with its engine running sound. But
at the same time I can be driving it that way and then it will
just drive regular and not have trouble with riding on the
road regular when I am on flat ground. Anyways I am pretty
positive that it's not having tranny problems cause I have
had the tyranny rebuilt at a transmission shop and it also
came with a year warranty so if I think my tranny is starting
to fail again I'm able to take it back there to make sure of
any problems. I was thinking it was having fuel injector or
filter issues. Or it was having maybe spark plug spark
problems or something. I am not a mechanic for sure so I
cant trouble shoot issues but if I can get someone to help
me figure out what I might need to do then I can for sure
take care of fixing what's failing unless it's an extensive job
to do. But if it's something I'm able to change out my self
then I wanna fix myself. Please if anyone can help me
narrow down my problem it would be awesome to have
some feed back. Thank you.