95 E320--it pays to think first
 

95 E320, 104992 engine, 92,000 miles, new wire harness, new head gasket

CEL on about two weeks ago. Clear codes, drive, recheck, reclear......Check again this morning. Consistantly get codes for upshift delay, EGR, and air injection pump. (diagnostic module 26, 5, and 4)

Seems very unlikely to have three problems show up at the same time on a car that gets meticulous maintenance. Then it occurs to me that all of these items have one thing in common--they require vacuum. Sure enough, vacuum hose on top of intake manifold had come loose. Reattached, problem solved.

Hope this helps someone else.

great deductive reasoning well done.proving once again that every thing on a car is logic there is no emotion involved[except by the person attempting to logic out the answer].

We have that in the archieves..
As David said, coupled codes sometimes have a common source. That line was originally plastic and they dry up and crack..replace the line w/stabdard rubber vac hose.
The line feeds the SOVs for EGR and AIR, so any combo of those codes and knowing about the plastic breakage leads you right to that hose.
Do watch for code 26 re-appear.. Common 124.032 shift cable element leak after SOV..