89 100q diag Help requested

[David G]

  I would appreciate some ideas on fixing a problem with an 89 100q.
It starts fine, runs fine for a minute or two, then falls on its face.
Stumbles and down on power for a few minutes untill the car is starting to
warm up, then suddenly like someone flipped a switch, it runs fine again.
   The car has an unknown history and there are signs of someone trying to
cover up the problem.  THANKS Scott, as the site helped me read codes;
however, I only get 4444 (no codes set).
Here is the interesting part, the car runs just as good with the DPR
unpluged!
So I am thinking someone richened up the mixture untill the DPR didn't
matter?
  If it were not for that the car goes from running poor to running right
instantainously, I would think the problem would have it's cause in a temp
sending unit and may replace them anyway (Is the 4-wire connector under the
coolant hose the first best bet?)
   Thanks for your thoughts
I will be making sure I have read every page of Scott's site
  Dave G