Hey everyone,

My 1994 Limited has an interesting problem/problems.

1)    It sounds like there is noise in the valvetrain, cylinder 4 (drivers
side, closest to radiator).  A "metallic clatter" sound can be heard all the
time (startup, driving, highway speed, etc.).  At this point I do not know
if it might be a collapsed lifter, or a problem with a pushrod or rocker
arm.  The motor runs "fine", but is very lacking in power, and does not have
a smooth idle or operation

2)    The exhaust "pops" like a cylinder is misfiring, and the sound
coincides with the metallic sounds coming from the engine (i.e. the sounds
occur with the same timing and frequency).

3)    The truck shudders quite a bit with "light throttle" at highway
speeds.  Either backing off or accelerating harder reduces the amount of
shudder considerably (back to the "background vibration" that occurs even at
idle).  I do not notice this at speeds less than 50k.  It does seem to go
away if I shift from OD to Drive....but I don't know if that relates to the
RPM of the motor, or if it suggests a transmission issue.  The car also
"clunks" into reverse, and I have read that U-joints may be the problem.
Could that relate to the shudder at highway speeds as well?

So far I have done the following:

-replaced spark plug wires and plugs (and yes, I wired the plugs correctly,
taking into account the weird order on the coil)

-removed, tested, and cleaned all fuel injectors to ensure fuel delivery is
occurring (replaced upper and lower fuel rail gasket at the same time)

-tested for spark (spark is very strong from wire to plug) in questionable
cylinder

-I have also cleaned the MAF and IAC a couple of times now to ensure they
are working properly.

-changed oil, ran 2 cans of "valve/lifter quieter" additive, then changed
oil 350 kms later and used 20w50 oil (no change in problems)

-had all tires rebalanced (they are quite new tires on all 4 wheels)

So I think that I have a valvetrain problem, and am wondering if improperly
opening valves is causing a misfire-like condition.

As far as I can tell (running engine with #4 spark plug removed) gas is
entering the combustion chamber (the air being expelled from the spark plug
hole reeked of fuel), and there is definitely adequate spark.

Sooooo.....the question is what to do next.  I am thinking about pulling the
valve cover to see if something obvious is broken (I picked up a used rocker
shaft set and pushrods from a scrapyard just in case).

If the lifter is collapsed, I presume there will be lots of play between the
rocker arm and pushrod?  If this is the case, can someone tell me
definitively if I have to pull the head or not to replace the lifter?  The
AutoZone web manuals say no, but an article I read on a Ford website said
yes.

And any suggestions on cheap replacement lifters?  Apparently they are
$70-90 EACH!!

I was told that "the lifters have a teflon cap that can fall out with age,
causing valve clatter, but this is just to be expected".....however even if
that is true (can anyone verify?) why does my motor run poorly and exhibit a
misfire condition?

Thanks in advance for any suggestions.  And if I am way off....please point
me in the right direction.

Chris