Hi folks

Thanks again for all the help on my previous thread.  My truck still
runs like crud, though I now see a pattern which may help.

Truck is a 96 F150 with a straight 6, fuel injected.  Symptom is it
starts fine when cold, and actually runs OK until it gets to operating
temp.  Once at temp, the engine stumbles badly when I give it more than
1/2 pedal on the accelerator.  More run time, and almost any gas makes
it run like it's on 5 cylinders.  Restarting when hot is almost
impossible, but a cold restart is fine.

Here's what I've done so far:
Replaced - plugs, air filter, oil, fuel filter, cap, rotor.
Removed and sprayed down 5 injectors, replaced one because my father in
law broke it (long story)
Checked vacuum at the brake booster port on the upper intake manifold.
Reading very steady 20 at idle, accel drops to about 5 and quickly
rebounds back to 20.  When I hold a higher RPM it drops very little.  I
don't have a tach, but I estimate the RPM to be around my shift point.
Tried various points, higher the RPM, less vacuum.  But the lowest it
gets to is about 18-19.

Vacuum readings seem to rule out clogged exhaust, though I may be mistaken.

I also pulled the throttle body and cleaned the heck out of it.  Used
1/2 bottle of SeaFoam cleaned through PCV hose, let sit about 10 minutes
and ran it out at idle.  Repeated again, this time letting sit for
several hours.

Codes - I only have the original list of codes.  They list
All O2 sensors reading a lean condition
Crankshaft Position Sensor not working.  (I missed this one before)
Misfire cylinder 1

Can the crank position sensor be causing this?  I don't even know what
this would do in this vehicle, as I have a conventional distributor with
rotor.

I'm at a loss as to what to change next, though maybe I should be
replacing the other five injectors.  The hot vs. cold conditions aren't
making sense to me though...

Thanks,
-ben