Hi Jim,

Mea Culpa - not intending to start a flame war, just respond to the
original poster's request.

All of the persons I know with IA are also A&Ps. As you correctly
state, many skilled A&Ps can replace an existing component with one of
a different manufacture and record it as a minor change in the logbook.
In my own experience, some A&Ps are more skilled or motivated than
others in making logbook entries.

I have indeed installed equipment in my plane, under the supervision of
an IA A&P. This work was recorded in the logbook, and a form 337 was
completed and sent to OK City. The 337 is hardly a paperwork blizzard.
It is one page, with standard blocks for information on the front, and
a space on the back to describe the change. In my own case, it was
pretty straightforward. I'm sure others have run into problems of one
sort or another with the 337.

Of course you are correct and precise about the yellow tag meaning that
it has been checked to specifications. Airworthy parts have either PMA
or TSO. The equipment I installed had PMA and a yellow tag (since it
was not new equipment), which I stapled into the logbook.

Brian