Mis fire

I have an 01 F-150 4.2 with 200,000. It recently
developed a miss over the last month which, like
an idiot I ignored. This one on for about a month
until finally within a span of about 3 days it got so
bad it was on drivable but I was able to limp it back
to the driveway. My code reader said P0302 and
P0304, cylinder misfires. This happened once
before in a Ranger I once had and it turned out to
be the coil pack.  So I went ahead and installed a
new coil pack new plug wires and new plugs, but
no help. The plug from cylinder for didn't look too
bad all thougj definitely time to be changed but
plug 2 was completely gummed up with what
looked like burnt oil maybe? I don't think it was
carbon. So next thing I did was put a fuel filter in. It
was pretty bad, in fact it was really bad . It  started
right up and reved strong, real smooth no miss,
although it seemed to idle a little rough. I put it in
drive and took off, it really ran, smooth, accelerated
hard......for about 200 yards, then it would die when
I try to accelerate but I was able to limp it back
home again. I've started it a few times since then
and it revs hard in park. But as soon as I put it in
drive and try to accelerate, it wants to die. In all
honesty  I've had to run it out of gas a few times
and I've been running a lot on empty. The code
reader also said.P0171 system too lean bank  1.
What do you think Gurus?