Barely-running '89 90q

[DePenning, Charles [EPM/MTN]]

Well this has really turned into a stumper.  Some of you may recall the
problem I'm having with my 221k mile '89 90q- in short, it runs like it is
missing on at least one if not two cylinders.  Starts like crap, runs like
crap when warmed up. This behavior started suddenly at highway speed, with
no indication of this before.  No power, and the exhaust smells pretty rich.
Here's what I have done:
Checked spark- OK
Checked compression- OK
Checked TDC on cam compared to flywheel- OK
Checked fuel system pressure(s)- OK
Checked fuel pump delivery rate- OK
Checked O2 sensor operation-at least attempts closed-loop
Checked cat- not plugged, but I hollowed it out anyway
Checked for vac leak- as well as I could, hoses look ok
Pulled Codes- 4444
Pulled out and tested injectors- thought I had it here.  All five really had
a bad spray pattern.  Like little needles.  So I ordered up five new
injectors from Blau, put 'em in (and cleaned up a lot of crap under the IM,
gave the IM a nice coat of paint, valve cover gasket, painted that
too...sure is pretty now).  Spray pattern looks great now, so I installed
them with confidence that this would solve all of my problems.  But noooo.
Still runs the same, maybe a little worse.  Argh!  I'm getting thin on ideas
now.  Would a big vac leak cause this behavior?  I am just baffled by the
fact that it ran great for a good long while and then suddenly crapped out.

Please help me keep my sanity!

Thanks in advance-

Charles DePenning
'89 90q
'84 4kq
'83 5kT