4kq acceleration issue

[Rory [Armodis.List]]

Hey audifans

I have a stock 85 4000 quattro that needs a lot of love =)  Based on a
couple references from audifans, I believe the car has an Inline 5
2.2L 10V CIS-E.

- The valve cover leaks and the lifters clack pretty bad.
- It idles high, usually a little above 1000.
- It has some trouble starting in the cold.  The colder it is, the
harder it is to start.
- I have to give it some gas to get it to idle steady but then its good to go.
- Sometimes it will almost stall until I get the car moving and then it's ok.
- The temperature gauge usually sits between the 1/2 to 3/4 mark
unless I have the heater on and then it drops down to between 1/4 and
1/2.
- The motor diesels.

The fuel pump, fuel pre-filter, and fuel filter have all been replaced.
I do not know when the plugs, wires, cap and rotor were last replaced.

Last night the car suddenly started having acceleration problems in
any gear.  I kept the RPMs above 4000 and the acceleration problem
seemed to go away long enough for me to get on the highway and get
home.  This morning and through the day the car seemed to function as
it usually does.  Tonight the acceleration problem came back and
didn't go away.  I limped it home and could smell something burning,
but didn't get a good whiff.  I think it was plastic like.

In looking at the Bently it seems this could be caused by a leak in
the air intake system, differential pressure outside of tolerance, or
several other things.  In searching through the archives I found
several references to the air intake leak and one about the oxygen
sensor.  I tried removing the oil dip stick as recommended in a post
from the archives to test the air intake issue, but that didn't change
anything.  Several posts are in reference to turbo motors, so I'm not
sure how that plays into things.

I know the car has quite a few issues that could cloud what is causing
the acceleration problem, but any ideas on where to start or what is
most likely to be the problem would be deeply appreciated.  If there
is anything I *must* do to narrow the problem down please let me know
(ensuring the idle screw is tightened down?).  I'm saving my pennies
for a motor swap, so I'd be happy if I could just get it running
fairly normal again.  Hopefully long enough to make it through
snowboarding season =)

Thanks in advance!
Rory