<We all know what causes the egr code (plugged up inlet pipe), but I wonder why these cars are so hard on these upshift delay valves? Weird.>
The egr plugged pipe is infamous on 104s, but one should keep in mind that there is also an up-graded EGR valve to replace an earlier one [ sticking was the prob w/original]. There is a TSB on it.
The simple test for blockage is to apply hand vac, [ about 15"]
to the egr at idle and watch for rough idle and egr Snap back when releasing vac. Pipe block will show no idle difference
[Remember , the egr is not energized at idle. So some rough idle problems can be a stuck egr] But that is another complaint...
The up-shift element and cable also went to a newer part, but
it is also possible to have a cable mal-adjustment trip code #26.
Best to check vac. procedures at the sw/over valve first, etc.
Some prefer to run the trans in 3rd for warm-up and BB the shift delay...me included.