Rough Running 90q

[DePenning, Charles [EPM/MTN]]

Hiya, I'm looking for some technical help with my '89 90q.  Here are the
symptoms:  Starts ok cold & warm, but runs very rough, like it is missing on
one or more cylinders.  It idles ok some of the time, then devolves into
roughness, shaking, sputtering.  If I rev it up a bit and hold the throttle
at a set position, say, 2500 rpm, it smoothes right out, but getting there
is rough.  Driving- no power.  Moving it around my driveway is an exercise
in patience and lots of revs.  This happened suddenly-  I was driving at
highway speed and it just started this behavior and it's been this way for a
couple of weeks.
Here's what I have checked:  Pulled a 4444 from ECU.  Fuel system pressure
great, good bleed down pressure.  Great compression for 234,000 miles,
across all cylinders.  Plugs look good.  Pulled spark plug wires off one at
a time, no discernable difference.  Air filter ok.  Pulled oil filler cap
off, didn't die right away, but started getting there.  Visually checked
vacuum system for leaks (not that that says much).  Tried the propane torch
vac leak detection method- no increase in idle speed noticed.

So, I've got a couple of ideas:  blocked cat, big vacuum leak that I haven't
found, one or more plugged injectors.  The fact that this started so
suddenly is what is throwing me a little into the realm of blocked something
or ripped hose somewhere.
  
Whatdya think?

Thanks in advance!

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